Vega began her Hollywood voyage portraying the daughter of Burt Reynolds in the laid-back television sitcom "Evening Shade" (1990). Although the series lasted for only one year, the experience proved to be invaluable to the young rising star. She made her feature debut in 1994 as the picture perfect daughter in the family comedy "Little Giants". In 1996, she portrayed JoAnne Thornton, the younger version of Helen Hunt's character in the blockbuster action feature "Twister."

Vega would continue to rack up television and feature credits for an additional four years before receiving the role which would ultimately accredit her as a contemporary action hero. That role came in the form of Carmen Cortez in Robert Rodriguez's blockbuster action feature "Spy Kids"(2000). Vega played one-fourth of the Cortez family who has set out to save the world. "Spy Kids" went straight to number one its first weekend out and immediate plans were made for its sequel.

In 2002, Vega returned as Carmen in "Spy Kids 2 : The Island of Lost Dreams" and once again in 2003 for "Spy Kids 3-D: Game Over."