Mexican filmmaker Alfonso Cuaron is receiving considerable praise for his coming-of-age road picture, "Y Tu Mama Tambien." But why is making a better, less cartoonish version of "Road Trip" or "American Pie" an achievement?

The film is being distributed unrated, but it hovers close to earning an NC-17 label. Unlike the coy, winking come-ons of Hollywood studios, it is unflinchingly graphic and sexual, a more honest approach to its casually erotic tale. And Cuaron makes some offhand socioeconomic observations about the haves and have-nots of his country, but they are no more profound or surprising than the central narrative.

Tenoch (Diego Luna ) and Julio (Gael Garcia Bernal) are two hormone-raging 17-year-olds, buddies despite the fact that their families come from different economic worlds. Casually wealthy Tenoch has a politically connected father who is conversant with the president of Mexico, while Julio is distinctly lower-middle class. But the distinction seems lost on them both.

The two might well have spent their summer lolling by the pool if Tenoch were not forced to attend a family wedding. There, the two of them meet Luisa, an attractive married woman about a decade their elder.

Still, the boys flirt with her, bragging that they know of a remote, pristine beach called Boca del Cielo (or "Heaven's Mouth") that she would surely enjoy. Days later, after she learns that her husband, Tenoch's cousin, has been unfaithful, she calls up the teens and agrees to join their beach trek. The only hitch is that they know of no such beach.

Yet off they go, not quite believing their good fortune, jockeying for Luisa's attention and affections, which turn out to be surprisingly available. The teens' attraction to Luisa (particularly as played by the steamy Maribel Verdu) is easy to understand. Presumably, her response to them goes beyond mere jealous reaction, to a connection with their carefree youth that she sees slipping away from her. In any event, it still plays out like a generic male fantasy without sufficient dramatic motivation.

"Y Tu Mama Tambien" is impressive visually, as the peripatetic trio sees vistas of poverty just outside of their station wagon's windows.

Ultimately, predictably, secrets get revealed, resentments surface, lessons get learned, and the three go their separate ways, sexually spent and even a little wiser. For all its attempts at a greater honesty in the genre, "Y Tu Mama" sticks to the usual clichs.

"Y Tu Mama Tambien" is not rated but would probably receive an NC-17 for graphic sex, frontal nudity, language and drug use. Running time: 105 minutes.