I think flying is generally cheaper if it's just you, and you book at the right time, just keep watching the prices starting several months in advance or wait for a special deal or promotion to come up.
If you are driving from the LA area, it's just going to depend on the car you have and how many people you are going with. There are three basic routes involving the 5, 15 (crossing over to the 5 once you get out of LA), and 101, in good weather the 5 route through the Grapevine and Pacheco Pass will probably be the quickest unless you are starting from eastern LA county. It's not a horrible drive, even the most time consuming route up the 101 takes maybe 7 hours tops (unless there's weather, bad traffic, etc.)
Also if you are in California the train or bus might be an option, I know there's a route that goes from Union Station to San Jose but I've never taken that one... don't know how efficient or reliable it is.