She's 24, ambivalent about her job, and has the sort of apartment in which a Dukes of Hazzard lunch bucket qualifies as an objet d'art. Helen Childress seems every inch the disenfranchised Generation Xer-except that a few blocks from her Los Angeles home there's this billboard with her name on it. The sign touts Reality Bites, the movie Childress wrote about postcollegiates searching for economic and emotional sustenance. Childress, raised in Houston, had the compleat baby-buster upbringing. Parents? Divorced when she was 14. Culture? ''I know every single episode of Good Times.'' Heroes? ''The thing about this generation is that there's nothing to believe in. I feel like God is Jim Bakker, the country is Watergate, and family is a TV show with Kristy McNichol.'' In 1987, on the strength of her poetry and photography, Childress bagged a college scholarship sponsored by Ogilvy & Mather, the advertising agency. She chose the University of Southern California's Filmic Writing program, mostly for its financial aid. ''I really had no interest in screenwriting,'' she says. ''I wanted to be a poet. But poets don't make any money.'' Childress caught on fast. Her first screenplay, Blue by You, found its way to producer Michael Shamberg (The Big Chill), who was trying to develop a movie about twentysomethings. Impressed by Childress' knowledge of Xer arcana, he commissioned her to write what became Reality Bites. The script, Childress estimates, went through 70 rewrites during its three years of development, during which she worked in a theater box office and moved to an Arizona trailer park with her husband, screenwriter Carlos Brooks. When TriStar Pictures put the project into turnaround, Universal Pictures stepped in. Although she's currently adapting Ellen Gilchrist's Drunk With Love for Interscope, Childress is wary of Hollywood. ''I don't even like the business that much,'' she declares. ''I know this sounds totally naive and idealistic, but I would rather get a job at Kinko's and write poetry than be in a position where I feel like I'm Willy Loman.'' Now that would really bite.