I'm staying in La Jolla for a few days and spent a lot of time scouring this board for info. Given the raves for Tapenade I felt like we had to go, but I just couldn't bring myself to spend the cash. After finally giving up and typing 'cheap eats la jolla' or something into google I discovered that Tapenade has a special prix-fixe lunch deal every day for 17.95 that includes one main course and one appetiser. I just got back today and that's probably the best meal for under $20 I have had in my life, hell it would be the best meal under $40 I've had. The duck confit with carmelized onions and truffles was flawless, and my girlfriends au poive was way above average. Of course it just makes me jones for the full dinner and the tasting menu, but if you're considering Tapenade and balking at the price definitely consider a lunch -- it was amazing.
Also on the save money and eat great food front, I ate in the bar at George's on The Cove and again I felt like I was cheating -- I had the thai fish stew which was incredibly creative and tasty, and a very impressive ceviche for starters. They don't just serve the light menu on the roof, it's in the second floor too.
Anyways, so far so good. Now on to find some great mexican.