Here's a quick rundown of some CA archetypes (mostly Southern CA related) and their usual uniforms:
Surfer/beach bum: Board shorts (baggy) with surf/skate brand T-shirt/tanktop and Rainbow flip-flops (optional hoodie and shades)
Hypebeast: Outrageously colored sneakers a must, baggy/saggy jeans, LRG hoodie or similar, fitted cap (bonus points for matching outfit colors to sneakers)
Jerk (referencing the hip-hop movement): similar to Hypebeast, but skinny jeans. Emphasis on the skinny jeans. See video: http://www.youtube.com/watch?v=POPP-Aoo8Po
SoCal Clubber: all about the brands, Ed Hardy, Monarchy, True Religion, Rock & Republic, Antik, throw on some square-toed shoes, and faux hawk that haircut. Fake tan for the win.
Retiree: Hula shirt, khaki shorts, flip-flops, big straw hat (not even panama status, think bigger: http://www.amazon.com/DORFMAN-PACIFI.../dp/B000UJCBH6
That's all I can think of for now, let me see if I can come up with a few more later.