I 2nd the Griffith Observatory, that view is dope.
Ok, for restaurants. Try to make it something you haven't had before, you know, the "only in L.A." spots
So,
#1. I'd say Pinks if you dig hot dogs.
http://www.pinkshollywood.com/
#2. Something a bit more upscale for desserts and drinks? The Bonaventure Hotel, there's a revolving bar (yes, it's spins son) on the 36th floor.
http://www.yelp.com/biz/bona-vista-lounge-los-angeles
#3. Mario's Peruvian will have the BEST food outside of Peru, and it's relatively cheap.
http://www.yelp.com/biz/marios-peruvian-and-seafood-los-angeles
#4. Don't do the walk around Hollywood Blvd. It's all bums, tourists, and fools in spider man costumes trying to make money by posing for pictures. BUT, you can take a tour to celebrity homes, people usually do that a lot.
http://www.starlinetours.com/
#5. Downtown L.A. has this event every week called ArtWalk. People walk around, drink, browse through different exhibits, and all the gourmet food trucks come out.
http://www.downtownartwalk.com/
#6. Since you're doing the SD Zoo, how about:
http://www.aquariumofpacific.org/
#7. In my opinion, the best burgers in L.A. are: Umami Burger
http://umamiburger.com/ or kitchen 24
http://www.kitchen24.info/Home.html
San Diego:
Anything in the Gaslamp District
http://www.gaslamp.org/
I got a whole bunch of suggestions, just let me know what you're looking for.