A fiercely proud Italian-American, his band, Calexico, were named after a town of the Mexico-California border and have made a virtue of crossing the boundaries (both musical and ideological) that keep cultures apart. "That's fantastic, " says the New York-born percussionist of Ireland's new-found multiculturalism, "there may well be a lot of growing pains with such change but there will be so many benefits as well."

Along with a myriad of collaborators, guitarist/singer Joey Burns and Convertino have for the past decade resisted definition with Calexico, even if they are constantly (and lazily, according to Burns) referred to as a tex-mex altcountry outfit.

Put simply, Calexico are the hippest desert indie band on the planet. Well, the only desert indie band on the planet. Born out of the alt-country explosion of the mid-90s that saw Lambchop, Ryan Adams et al gain previously elusive crossover success, they are a group you love to tell the unconverted about; one you are quite happy not to see gain crossover appeal. Unfortunately for Burns and Convertino, who met and first played together with a band named Giant Sand (which despite the duo's absence is still at the forefront of what is being dubbed New Weird America), such crossover success may have to wait until their next (and sixth) album. It's not that their latest album, Garden Ruin, isn't any good, it's just that it is an unremarkable, largely indie/country rock affair. Sure, the playing is subtle and dexterous, the rock tracks powerful and erudite, but Calexico fans may want something a bit weirder.

The difficulty is that Calexico have always resisted being pigeon-holed for the very qualities that make them so unique: the sound of rattlesnakes, the endless Arizona sky, Mexican border rats and mariachi bands and horns.

The ghost of Ennio Morricone's music looms large and at times unwanted over Calexico, perhaps because Convertino and Burns started off playing low-fi dust rock with their 1996 debut album Spoke.

The Tucson duo's latest album pays homage to their beginnings; just Joey singing with a guitar and John pounding and brushing the drums. For Garden Ruin's release on this side of the water the two of them play a showcase gig in a basement in central London for a collection of friends, fans and journalists. It's a fairly down-tempo, intimate affair as Joey expresses gratitude to the 30 or 40 people gathered to hear Garden Ruin songs for the first time. "This is just a thank you to all those who have supported the Calexico project for the past 10 years, " he says after a stripped down performance of the album's opener 'Cruel', "and here's to the next 10."

Amid the intense, quiet-loud performance there is a feeling that things have indeed come full circle for a band that has made a virtue out of collaborations, even if the latest album does disappoint some fans of 1998's baroque The Black Light and in particular, their third album, 2000's mariachi-inspired Hot Rail.

"There is likely to be some surprise, " says John after the gig, "but this is an album we felt we had to make for ourselves. We just wanted to get back to basics. It's a lot of work putting together a mariachi band and bringing a string or brass section on tour. This time it's just the two of us and, as a percussionist, it's exciting to work in this way. There's no hiding behind big sounds or electronica. It's right back to how things were when we first started out."

Not exactly. Garden Ruin sees Calexico take inspiration from sometime collaborator Sam Beam of alt-country stalwarts Iron & Wine and sees them tackle political issues with more gusto than ever before. The re-election of George Bush and the war in Iraq, the environment and US immigration policy are the chief bugbears. Convertino, who smiles when he admits to having two cars and an enormous fridge, still feels aggrieved by Bush's second election victory. "No one I know voted for Bush but the funny thing is, where we come from there is a fiercely Republican streak, " he says. "It is intensely conservative, probably because of its proximity to Mexico, so we are not exactly in step with the general feeling.

Around the time of our last album's release a lot of people were angry that their votes hadn't been counted and what was really amazing that four years later all this seemed to be forgotten and he was re-elected. People felt hoodwinked yet the war in Iraq had stoked enough fear to keep the Republicans in power."

This kind of attitude makes Garden Ruin easily the band's most angry work to date, with Burns' voice sounding more bitter and vitriolic than before.

"We could have kept going with the mariachi sound that people often identify us with but we have never been about milking a certain sound for commercial gain so this record is for us, " he says. The closest Calexico have come to mainstream success was with their excellent cover version of Arthur Lee and Love's 'Alone Again Or' and some soundtrack work. Not that Convertino, whose wife had a baby boy last year and lives in a house with a bit of land and two dogs, could care less. World domination is not exactly in the band's articles of association. The state of the environment is, however. Take this, from one of the album's best (and most recognisably Calexico) tracks, 'Roka (Danza de la Muerte)': "So close your eyes/Slow your breath/Dream of northern lights/Around this dance of death."

The garden of the world is certainly in ruin then? "Yeah, the environment is something that the US government is taking for granted. It's not politically expedient to focus on it at the moment so it has been lost in policy but it's not going to go away. We will be paying for it further down the line, all of us."