The sweeping four-star driveway of the Tivoli Hotel, Lagos, began to rumble with the arrival of an incongruous visitor; Betsy is the least athletic of The Mountain Bike Adventure team, with a fat yellow arse and some rusty innards that sound like they're about to fall out. But she also has the most character; she's their battle bus, and bears the scars.

Despite attracting the attention of the surrounding golfers, as their clubs rattled to her gravel-tones, her arrival put me at ease. The elegant foyer and ubiquitous polo shirts and slacks were making me think we were in the wrong place until Jim Carroll, Betsy's boss, brought her roaring to join the links-bound luxury minibuses, like a whore at the ball.

My girlfriend, Alice, and I were in Lagos through a quirk of Groupon, and joining Jim and Betsy through determination. Being relatively new to mountain biking has never put us off venturing in search of foreign soil to tear up. We like our adventure sports to be more adventurous than sporty; I always thought adventure should include a little culture, a little exploration and a generous dose of adrenalin. And there's no reason a lack of ability should interfere with that heady mix. Luckily for us Jim was on hand to keep us on the not-so-straight and narrow.

Portugal's Algarve coast is known as a beach-destination, popular with golfers, retirees and those Brits who can't go a week without a full English breakfast. It's dotted with the kind of self-contained resorts that make me feel claustrophobic and stifled. And you're not encouraged to leave except by organised boat tour. So climbing out of Lagos on Jim's excellent Saracen Ariel's was a liberation.

The Atlantic sank far below our wheels and the low autumn sun set fire to towering sandstone cliffs and the marshalled ranks of seastacks, concealing isolated coves and beaches, empty of tourists during the late season. Only storks and cormorants kept us company.

The route was classic coastal cross-country; lots of ups and downs, salt-weathered scenery, and interspersed with re-purposed fishing villages. The majority of the ride was on natural paths worn by pottering tourists exploring the coastline, but in some places Jim has extended or modified the clay-heavy ground - up to 45km worth of back-breaking work in Portuguese heat.

After an hour of serene cliff-top pedalling past aloe vera and Roman fish-salting pits, we descended one of Jim's creations, a technical downhill into Praia da Luz, featuring water-ruts baked hard into the clay, a handful of loose switchbacks and a smattering of rollers and kickers. Cracking riding anywhere, but when it leads directly to a tropical smoothie right on the beach front, unbeatable.

Then more of the same until the still-functioning fishing village of Burgau for lunch; promontories and rock shelves overhanging the ocean and more sandstone seastacks giving the effect of Utah-on-Sea, through cacti-strewn rock gardens and over the foundations of crumbling buildings. If the day lacked in aggressive riding it was more than balanced by the sense of an exotic excursion. Alice and I have put in our time in search of flow in the UK's peerless trail centres; but isn't this the essence of adventure sports? Regardless of ability it's the chance to see the world from a different vantage point - like skiers getting away from the piste to embrace the whole mountain.

Having explored the surrounding area, the town of Lagos now seemed more alive to us.

We could see it in context, recognise the Algarve characteristics and the effects of its surroundings. But we still needed help from Google to find a decent restaurant. The pedestrianised streets are lined with places to eat, and on the strength of menus and prices there is little to choose between them. A little research however made the difference and we discovered Don Sebastiao and Mullens - two places with genuine charm, superb service and excellent food - and no more expensive than their imitators.

Jim made a bold claim before our second day; "Betsy is a monster, but April is a ballerina". The two ladies are twins, and I literally couldn't tell them apart. The subtle distinction was lost on me, and on the golfers, as April shook the Tivoli foundations as Betsy had the day before, without a hint of a pirouette or a plie.

We were heading inland to the Serra de Monchique mountain range, the highest of which sits 902m above the town of Lagos at sea level. 20km in April did nothing to enhance her Swan Lake ambitions, but we certainly fell for her charms as she ferried us four times to the summit for downhill laps of a superb 10km trail, again built by Jim.

From the summit the eye could take in a wondrous diversity of landscape with a single sweep; in the far distance, beneath ominous cloud, was the twinkling ocean and the sandy fringes of the coast. Immediately below us, densely wooded hillsides, and lower down ancient terraces were cut into the hillsides by Roman occupiers and still farmed today. As if to round off this geographical vignette, the hills are topped with wind turbines to represent the present and the future of the land.

It was among these modern monoliths that we plunged headlong into a day of relentless gravity,

which was going to be very different to the previous day's jaunt. We were immediately bouncing between loose rocks and deep grooves, with the belligerent bushes of an arid climate flicking at our calves. "I like getting my legs muddied and bloodied, it makes me feel like I've done something" said Alice as I scratched my shins with a whine.

The stones got looser and the boulders got bigger and Jim's bunny-hopping tips came in useful. We hit a section of Roman road - forget wide straight avenues, this was a mountain road, and as narrow and windy as any purpose-built singletrack, and with the surrounding, angry plant life offering no soft option compared to the readily-uprooted cobbles.

With the landscape changing faster than I could pedal I half-expected to see treetop sword fighting as we entered a eucalyptus glade that was straight out of House Of Flying Daggers. Just as quickly we switched to a leaf-carpeted forest, made equally bizarre by the fact that the gnarled old cork trees had been stripped of half their bark and were naked from the waist down.

We skirted around the terrace-farms and hit the road for a few minutes, to re-gain a bit more height before diving into my favourite part of the day; much more clay and much less rock combined with a log drop and berm after berm in the pump track section. While I was simply trying to react quick enough, Jim was almost digging irrigation channels with the ends of his handlebars.

It's greatly to Jim's credit that these lower sections are so smooth and flowing but he never set out to build a trail centre. More impressive is what came earlier; a trail of unbelievable variety, which manages to retain all the characteristics of a natural ride.

On second thought, the most impressive thing is that it is all April-accessed. Our first descent had been slow; hampered by the endless photo-opportunities and the fact I seemed to have forgotten how to ride a bike. But the uplift gave us all the benefits of a trail centre - lap after lap, learning the features of the trail, fine tuning techniques and lines - as well as the rugged adventurism of a natural ride in a foreign land. By the final descent I was starting to feel quite pleased with myself.

To round off the day, Jim took us further down the mountain on some very gentle firetracks where we passed orange trees heavy with fruit and half a dozen farms tended by solitary 70 year olds who had all the time in the world to stop and stare. With the terraces resembling paddy fields, monsoon-like clouds above and the odd banana tree coming into view I had a sudden feeling I was in South East Asia. Amazing that all this is so close to the golf courses and sun loungers of the Algarve.

For all the exhilaration of the day there is a special place in my heart reserved for that triumphant and smug return to the sleepy hotel. Staggering wearily through the foyer, muddied and bloodied while the golfers return with nary a hair out of place; yes we felt like we'd done something.