Valley Girl tells the story of Julie Richman (Deborah Foreman), a sweet-natured but shallow Valley Girl. After breaking up with her jerk boyfriend Tommy (Michael Bowen), she finds herself at her friend Suzi Brent's (Michelle Meyrink) party, which is described as "the social event of the season".
At the party, two boys from Hollywood crash the scene. One of them is the sensitive and adventurous Randy (Nicolas Cage), who immediately becomes smitten with Julie, and she with him. However, Julie's friends are not supportive of their relationship because Randy is from "Holly-weird" and they want Julie to get back together with Tommy.
Julie is faced with a dilemma - she must decide whether to follow her heart and be with the boy she loves, or seek the approval of her friends. Meanwhile, a side story involves Suzi and her stepmom (Lee Purcell) competing for the attention of Skip (David Ensor), the grocery delivery boy.