What do I do with my friends??

Hello everyone, I need your help!
I have a couple of friends (a married couple) coming in town today and staying a week. We are planning to do the zoo, the Padres, and a day trip to LA or Orange County beaches. Any other ideas? Any local San Diegans with recommendations on restaurants or things to do? They are on a tight budget, so I can't do anything too extravagant.