But what do you want to do in San Diego once you get here? Without a car, it won't be easy to get to most tourist destinations.
I would suggest taking the train, as the previous poster suggested. That gets you to downtown San Diego. From there you could take the trolley to Old Town, or you can walk down to the Embarcadero area where the Midway Museum and Seaport Village are located. Or you could take the bus to the Zoo/Balboa Park (but I think a taxi would be easier/more efficient).