In the sad, funny, sexy, and altogether marvelous Y Tu Mamá También, Mexican writer-director Alfonso Cuarón takes one of the oldest formats in the filmmaking handbook -- the coming-of-age road movie -- and gives it a passionate and personal renovation. On this astonishing tour through a Mexico never seen in travel brochures, a couple of teenage best friends baying with unearned sexual bravado persuade an alluring Spanish woman to come with them away from choking Mexico City to a magical beach they'll show her. (The title is a boyish taunt of its own -- ''and your mother, too!'')
Tenoch (Diego Luna, seen in ''Before Night Falls''), son of a rich and corrupt politician, leaves his fancy villa. Julio (''Amores Perros''' charismatic Gael GarcÍa Bernal), the poorer son of a working single mother, splits from his cramped apartment. Luisa (popular Spanish actress Maribel Verdú), the wife of Tenoch's distant cousin, and an ''older'' woman only when measuring the chasm between teens and 20s, impulsively takes the boys' jaunty offer, for reasons and secrets of her own.
As they meander, the real, gawky energy of adolescence intertwines with the sharp pains and pleasures of a modern Mexico as emotionally raw as the boys themselves. Teen sexual discombobulation -- and, for that matter, a young woman's own erratic lusts -- have rarely been portrayed so authentically, a credit to the natural actors as well as to the director of the superb 1995 jewel ''A Little Princess.'' Meanwhile, the exquisite cinematography from the impeccable Emmanuel Lubezki (''Ali'') is occasionally pleasantly shaken up by narrative hiccups inspired by French new-wave techniques.
''Y Tu Mamá También'' is so organic that the road trip, magical as it is, feels in a way realer than life. This remarkable travelogue tours a mysterious age and place that only an artist like Cuarón can locate on the map.