Though I live in the Los Angeles metro area, San Diego is quite honestly my favorite of the major Cali cities. San Diego is just so chill and laid-back.
LA is too congested and too busy; I’ve never really understood the appeal of San Francisco, I’ve found San Fran too cold, too cramped (it’s a very compact city), and the city has some very real issues that need to be addressed.
If the weather cooperates, I recommend Mission Beach. W and I went there when we went to SD. It might be a bit touristy, but I really liked it. Also found a good number of sand dollars while at Mission Beach.
Not sure if you’ve ever been to Cali, but the food here is mostly excellent (I have had a handful of bad meals in SoCal). I hope you’ll enjoy it in San Diego!