Like SoCal, I live in San Diego. I'd be happy to recommend any good spots in the area or answer any questions.
To start, I'd highly recommend Balboa Park. The Zoo is there, but so are at least a dozen pretty amazing museums. Even if you're not keen on going to a museum, the park itself is a great place to walk around. It is easily my favorite place in San Diego. (I happen to work on the edge of the park just west of the Cabrillo Bridge.)
If you haven't been, I highly recommend La Jolla Cove as well. The street you'll want to look for in your MapQuest/Google Maps/TomTom/Garmin is called "Prospect." That will get you right into the heart of the action. From there you can park and walk around. (Georges, the restaurant that SoCal mentioned earlier, is right on Prospect in La Jolla.)
I didn't see it mentioned, but I would also recommend Seaport Village which is located near downtown. It's got lots of shops and places to stroll with a lovely view of the bay and the aircraft carriers. If you go, I would also HIGHLY recommend that you take a tour of the U.S.S. Midway which is docked there as a floating museum. Having lived in Nebraska, it's not everyday that you get to tour an aircraft carrier.
Other spots that others already mentioned are the Gaslamp District (which is basically a sophisticated version of "O" Street in Lincoln and would probably appeal to a younger crowd), and Coronado Island (which is not all that exciting except for the Hotel del Coronado).
Also, a lot of people talk about the San Diego Zoo (which, again, is in Balboa Park), but I personally think that the Wild Animal Park (now called Safari Park, or something similar), is actually better. It is further north of San Diego in a town named Escondido, but is worth the drive if you end up renting a car.
For those that are coming, safe travels and welcome to San Diego!