Children's pool - Intersection of Coast and Jenner is where seals come to sleep and and play and such so you can see them for free.. Great sunset spot too.
San Diego zoo is amazing, and only a 15ish minute drive from La Jolla.
Balboa Park - Sunday afternoons has free music (can't remember the time) with lots of flowers and plants.
Sea-World
Old Town San Diego, has some orginial buildings from the 1800's.
If you are into fishing there are 1/2 and full day tours for not too much and we caught lots of fish.
If you are looking for a drive, make your way up to Julian and have a piece of Apple pie.
Restaurant recommendations are, Oceanaire (SD), Pamplemoose (Carlsbad), Crabcatcher (La Jolla), Carl Strauss (if your a beer drinker - La Jolla)
If you have specific questions feel free to contact me, we lived there for 18 months, and have only been gone from there for 10 months or so..