Southern California:
Ok I live in Newport Beach California this is a fun place. Nice beaches and clubs. This is s very sophisticated area. There in Newport there is Balboa island with a boardwalk and small carnival.
But if you want more of the "Surfer Scene" Huntington Beach is the place for you. This place has earned the title of Surf City "U.S.A."
Also the Crystal Cove/Laguna Beach area is a fun place to walk around in the famous "Hills" area. If you go down to these places it’s best to walk or rent a beach bike to get the full dosage of California Culture.
If you want theme parks Disneyland @ Anahiem is the best. It kicks all the other theme parks asses.
Also every Tom, Dick, and Hairy, vacations to San Diego and they judge California based on that. The areas I mentioned are the places to be.

Northern California:

If you wanna go up North More then Monterey is a good place. There is the famous "Canary Row" & "Fishermans Wharf".You can hit the aquarium. Or just go to the beaches there is tons of sea otters and sea lions swimming and lying on shore. Keep in mind the waters are colsd so this is more of a sight seeing place but still is a shit load of fun.

E-mail me if you have any more questions.

any town on the coast except Los Angeles. Seriously Los Angeles is so overrated there are other cities north of San Jose that just knock your socks off.. and the farther North you go the nicer it is.