Gael Garc’a Bernal rides with Maribel Verdś in 'Y Tu Mamá También.' Y Tu Mamá También Starring Diego Luna, Maribel Verdś, and Gael Garc’a Bernal. Directed by Alfonso Cuarón. Written by Alfonso and Carlos Cuarón. Not rated.

The first line of Y Tu Mamá También is said by Tenoch (Diego Luna) while he's lying on top of the girlfriend he's just had sex with. It sets the tone for Alfonso Cuarón's comedy, which, like a good many American comedies, gets its energy from the sex-obsessed antics of horny young guys. The difference is, the movie follows its characters' hormones in directions that our Hollywood movies wouldn't dare go.

Tenoch and his best friend Julio (Amores Perros' Gael Garc’a Bernal) are both facing a summer with nothing to do, and no one to do, with their girlfriends going off to spend the season in Europe. At Tenoch's sister's wedding, they spend their time hitting on Luisa (Maribel Verdś), a sexy Spanish woman in her 30s who turns out to be married to Tenoch's cousin Jano (Juan Carlos Remolina), a published author who wears white suits and gives condescending and incredibly trite tips on writing. Soon afterward, Luisa finds out what a pendejo she's married to and takes Tenoch and Julio up on their offer of a week-long drive from Mexico City to a pristine beach that's undiscovered by the tourists.

The movie's scarcely recognizable as something by Alfonso Cuarón. The Mexican director first gained attention in Hollywood with two visually opulent but narratively languid films: a shimmering adaptation of Frances Hodgson Burnett's A Little Princess and a modernized version of Charles Dickens' Great Expectations that might have been great if it had been a silent movie. Returning to his native country, Cuarón checks his highbrow taste at the border. There's a ton of both sex and conversation about sex, and all of it's as emotionally complicated as it's physically raw. The dialogue is laced with both profanity and slang peculiar to Mexico City in amounts that'll prove bracing to Spanish-speaking gringos. Cinematographer Emmanuel Lubezki (whose other credits include The Birdcage, Sleepy Hollow, and Ali) gave Cuarón's other films a golden tinge, but here he employs a hard-edged realistic style, with many outdoor scenes and others shot in natural light. There are no lulls in the storytelling, because there's always something to see on the road -- and it ain't all pretty.

That's a good thing, too, because the story's concentration on these three relatively privileged characters might have turned the movie myopic. Instead, Cuarón's camera leaves the characters on occasion and goes off on its own: a servant taking drinks to some exhausted mariachis during a wedding party, and a waitress bringing an order into a dank kitchen. While the characters are having a spirited discussion about penis size, we catch sight of federales with machine guns rounding up campesinos by the side of the road. The voiceover narrator (who, in the manner of the narrators in Amélie and The Royal Tenenbaums, imparts both large and small pieces of background information in the same dry tone) informs us of the sad fate awaiting a jolly fisherman who gives a boat tour to the characters, and tells us of the noble origins of Tenoch's name while we see Tenoch smoking weed as a prelude to taking Ecstasy. Tenoch and Julio's obliviousness to the conditions around them testifies to their arrested development; when they're held up in traffic by a demonstration, Julio's reaction is, "Left-wing chicks are hot, dude!"

These glimpses of the larger society in Mexico are just long enough to comment sufficiently on the characters without interrupting the rhythm of their story. Tenoch and Julio are infectiously charming in their immaturity and their zest for life, but they're tragically unable to handle the home truths about themselves that Luisa teaches them. For all their talk about girls, their banter and horseplay are pregnant with homosexual overtones that eventually come to a head. This, ladies and gentlemen, is where the American Pie films and their legion of Hollywood imitators are afraid to go, and their inability to be cool about the subject of male homoeroticism leaves them worse off, much as it does with Tenoch and Julio.

The resurgence of Mexican cinema would get more ink if their filmmakers all made the same type of film. If they did, the press could label their efforts a movement (like "Italian neorealism" or "French New Wave" or "Chinese Fifth Generation") and elevate their status while pigeonholing them. However, Mexico's directors are too independent of each other and too willing to pursue their unique visions, whether in their own country, in Hollywood, or even Europe. It's bad for their publicity, but it's great for their creative output, as directors from Guillermo Del Toro to Alejandro Gonzalez Iñárritu showcase the eclecticism and sophistication of their nation's cinema. With Y Tu Mamá También, Alfonso Cuarón proves himself to be both a mature storyteller and a flexible and extremely capable stylist. He's ready to join the ranks of the world's great filmmakers.