San Diego is the craft beer capital - so if you’re into that you have a ton of options (Stone is one of the oldest one and has a few nice locations in the city, Modern Times is my personal favorite). Also make sure to get some Mexican food while you’re in San Diego.
The Old Town in San Diego is a classical tourist spot. Cabrillo National Monument is a nice spot where you get a good view of the city and the ocean. I also like the Gaslamp Quarter for like just walking around (this one is close to the conference center). There are also some nice little cities up the coast (Oceanside is a nice little surfer town, Encinitas and Carlsbad have tons of small breweries, small shops etc - it’s imho awesome to just go there and stroll around). Liberty Station is also worth a short visit.
Balboa Park is pretty nice (and the weather is good). You can walk around or rent a bike. There’s also several good museums there and a semi-famous zoo (although I’ve never been to the zoo - so don’t know whether that is worth a visit)