I have used third party apps (spot hero and park mobile) to find great rates... I've parked in a ramp two blocks from the hotel for under $10.

But. 1) these don't get you in and out privileges
2) California is notorious for car theft.... Anything from Cadillac convertors to license plates. Though I've not had a problem, you do run that risk if you park in an unmonitored lot or garage.