Seriously, the possibilities are endless. SoCal is unique in that you can go surfing in the morning, skiing in the afternoon, and Disneyland at night.. there is such a wide array of locations, especially in a 10 day time frame..
I'd suggest you check out some books at the library and spend a fair amount of time finding what suits you. I grew up in that area and know it as well as I know Thailand.. so if you tell me what type of photography you most enjoy I can offer suggestions.. but there's just so much there I could lead you astray. Everything from tidal pools, wetlands, oceans, mountains, deserts, gardens, architecture, entertainment attractions, street shooting, Chinatown, Korea Town, Little Arabia, Little Italy, and other ethnic neighborhood you'd care to shoot. The river basin is unique, Santa Monica Pier, the coast highway (HWY1) all the way up through the redwood forest (spectacular) with San Francisco and Solvang (Dutch theme town) and other coastal cities of merit..
Properly planned you're going to have a great time!