Safe to assume you're coming for the ocean? Then I'm guessing you're looking for southern California if youre thinking about surfing. The bay area has great spots as well from what I gather but it's not exactly affordable. The central coast has some amazing spots like Santa Barbara, but it's a bit of a distance north or south to get to LA or SF... although it's a huge college/party town, so maybe that's what you're after.
If you're looking for socal and you don't want to go broke, Ocean Beach in San Diego is a fun/young area. Huntington Beach in Orange County and then if I wanted to be by the ocean in LA and not poor, I'd go for Redondo Beach. Venice would put you in a bit more lively area with more to do and closer to LA/Hollywood but the cost goes up substantially to be anywhere near the beach. Santa Monica is a bit nicer than Venice, but again, expensive to actually be near the beach.
Expect to pay around $700 for a bedroom in SD, $800 in OC or Redondo/Hermosa, and around $1000 - $1200 for Venice/Santa Monica (this is if you want to live walking distance to things to do and the beach.
If next summer in LA is particularly enticing, the Expo (metro) line is going to be complete by then and will run from downtown LA to Downtown Santa Monica. Culver City (expo line runs through) is more affordable, as is anything near the UCLA campus that will also be served by the Expo line by then. USC is served by the expo line already, but you don't want to live by USC.
But if you're just looking for beach and a party, Santa Barbara is a great place for that.