IN 'Y TU MAMA TAMBIEN,' BOYS DEFINITELY WILL BE BOYS.

Byline: Bob Strauss Film Critic

IMAGINE: a teen sex comedy with politics. Never in Hollywood, but not impossible in Mexico.

Its political consciousness is a prime reason why ``Y Tu Mama Tambien (And Your Mama Too)'' is such a fresh, exhilarating moviegoing experience. As lively and unruly as its 17-year-old protagonists, this Spanish-language coming-of-age story is also notable for the breadth of its scope, the dead-on persuasiveness of its characters' thoughts and actions, and its copious couplings (mostly bad) and nudity (mighty darn attractive).

The free-styling, gritty/beautiful realism of the piece is also refreshing, and comes as somewhat of a surprise from the director/cinematographer team of Alfonso Cuaron and Emmanuel Lubezki. The duo's American productions, the smartly done (and 180-degrees opposite from this) ``A Little Princess'' and the misguided modernization of Dickens' ``Great Expectations'' both suffered from a sense of formal overcontrol that sometimes spilled into preciousness, and often seemed to throttle any sense of spontaneity.

Going back to their homeland - and to a tone more in keeping with their first film there, ``Love in the Time of Hysteria'' - apparently liberated Cuaron and Lubezki's imaginations. With guys this creative, that is quite a thing to see.

Julio (Gael Garcia Bernal from ``Amores Perros,'' last year's world- class Mexican production) and Tenoch (Diego Luna, ``Before Night Falls'') are upper-middle-class best friends whom we first encounter making earnest love to their respective girlfriends. Then the young ladies head off to Europe for the summer, leaving the boys to brag, bust each other's chops and, the majority of the time, mope hormonally about some of Mexico City's most comfortable - but still boring - precincts.

A ray of excitement appears when they meet the Spanish wife of Tenoch's loser cousin at a fancy wedding reception. Improvising all the way, the boys try to convince the sexy, older Luisa (Mariel Verdu, seen on this side of the Atlantic in ``Belle Epoque'' and ``Goya in Bordeaux'') to accompany them to a fictional beach. A few days later, when personal traumas cause Luisa to tell Tenoch that she's ready for a swim, the guys shift into overdrive. The resulting road trip is to a place that both literally and metaphorically doesn't exist, the latter being the teens' erotic Dreamland.

Whatever her private woes, Luisa is more than hip to what's on the boys' minds, and enjoys using her greater experience to play games with the gamey contents of their manchild imaginations. But Luisa is not cruel, so she makes an effort to fulfill the boys' fantasies. But as she ruefully observes after jealousy and anxiety inevitably lead to, well, adolescent male behavior: ``Play with babies and you end up washing diapers!''

There are lines that good all through the script, which Cuaron wrote with his brother, Carlos, finely crafted but seemingly blurted out, and acutely revealing of a moment's feelings. But there is another series of lines, spoken by an off-screen narrator, that explain both character backgrounds and socioeconomic contexts. It's a risky gambit, potentially pretentious and something that, in lesser hands, could stall the narrative's momentum in its tracks. But Cuaron is able to make the dry narrator feel like a welcome and informed guide to the proceedings.

Indeed, these distracted sons of the international leisure class hardly realize that this ride through rural Mexico is a journey to a foreign land: their own. They may be too obsessed with Luisa and the truths they're confronting about one another to notice, but the audience sees the poverty, the embattled traditions and the bullying government soldiers pass along the side of the road as the love machine whizzes by.

``Mama'' has a few flaws. As preoccupied with bodily fluids as any American-baked teen film, it gives the impression that Cuaron is trying to shock for gratuity's sake a number of times. And 11th-hour character disclosures have the opposite effect; they feel pat when they should pack a revelatory wallop.

But these are minor lapses for a film that so wisely captures the exuberance and ache of growing up, and even more intelligently acknowledges that kids grow up into some kind of mean old world, whether they're aware of it or not.

Y TU MAMA TAMBIEN - Three and one half stars

(Not rated: graphic sex, nudity, language, drug use)

Starring: Maribel Verdu, Gael Garcia Bernal, Diego Luna.

Director: Alfonso Cuaron.

Running time: 1 hr. 45 min.

Playing: Showcase, Hollywood; Westside Pavilion, West L.A.; Monica, Santa Monica.