Look up "Star of India" if you like Maritime history. Balboa Park has a wonderful group of museums specializing in many different subject, Art, Aviation, Sports --among others Even walking among the buildings is like being in another time. Old Town is like being in a pleasant Mexican Plaza-- good food there. Anthonys seafood Grotto is a good place for fishy fare.
The SD Zoo is outstanding, as is Wild Animal Park and Sea World. Lots to see and do there.