Transamerica is blessed with, ahem, a ballsy performance from "Desperate Housewives" star Felicity Huffman as Bree, an L.A.-based pre-operative he just days away from final retooling as a she.

But the hospital visit is put on hold when Bree learns that, in his "he" days, he fathered a son and the young man, Toby (Kevin Zegers), a 17-year-old crime-prone gay street hustler, is now in trouble and in custody in New York. Bree heads east to the rescue, forcing a short postponement of the much-desired surgery.

At the police facility, Bree, never disclosing his/her paternity, passes him/herself off as a missionary, pays Toby's bail and gets the son released. Bree's trumped-up Christian calling aside, both share a mission to get to L.A. as soon as possible-Bree, so comfortable as a female incarnation, to go under the knife and Toby to go before the cameras as a porn star. Onscreen in situations like this, money must be tight and the car risky business. The unlikely duo buy a lemon, which encounters the requisite breakdown and forces a slow start. But once wheels are turning, the film gets rolling.

Bree means to unload Toby with his estranged stepfather in the South. Once there, Toby, of course, resists; the reason, Bree learns, is that he was a victim of child abuse. On the road together again, they make a variety of stops: a tranny coffee klatch in Texas where guys can really be girls; a stopover in New Mexico, where they are robbed of car and money but rescued by kindly Native American Calvin (Graham Greene, delivering a charming performance). He gets them as far as Phoenix, where Bree reunites with her prosperous but estranged family-flashily dressed, eruptive mom Elizabeth (Fionnula Flanagan, campily taking her character over the top), resigned Jewish dad Murray (Burt Young) and screwed-up younger sis Sydney (Carrie Preston).

When Bree takes an Arizona moment to finally tell Toby the whole truth, things take a bad turn. But, ultimately, it's still westward to L.A., where the film ends very satisfyingly and according to template.

Family-themed and something of a family affair (Huffman's husband William H. Macy is the film's executive producer), Transamerica delivers a plethora of pleasures: a bold approach to its sexual themes, a fine script, and terrific performances, especially from Huffman and Zegers. Pruning would have helped with momentum, as the ride does have its longueurs.

But with delicious scenery and a lively music track, Transamerica adds up to a well-tuned vehicle whose slightly grainy chassis, bumped up from 16mm, belies a low sticker price. But there's a road alert: Not blatantly commercial (in the way that My Big Fat Greek Wedding was) and not off-the-rails arty, Transamerica faces the soft shoulder of the tweener. Marketing to gay, hip and upscale crowds may avert that crash.

-Doris Toumarkine