As a native Southern Californian recently moved up to NorCal, I will attest that people say hella a lot. In fact if anyone from southern California is heard to say hella, we give them a hard time for it, in addition to laughing at the people who say it, probably because we feel we're above such slang usage.
I can't really think of much slang that I use, though "my bad" and "owned" might count. Here's an example that is limited to the people on my dorm floor: The people who like to smoke weed started referring to it as playing tennis. For example if the resident assistant is in the room, one person will say to the rest "Hey, you want to go play some tennis later?" everyone except the RA knows that they really mean smoke pot. It's become a running joke, and people have started to use it all the time when talking about it (there are a lot of potheads here) just so that nobody knows what they are really talking about. People also say stuff like "He's a star tennis player" and the like to talk about someone who likes to get high a lot.
