One of my ex-husbands lives in SD and really likes it. Says it's not like it's even California.
I have family in SD and LA (and SF). SD used to be the laid back LA (coastal LA, not inland desert). Had the best beach in the area. Now they are practically the same, but old town is a cool walkable city.
But there's definitely lots of similar areas in CA, most just aren't also a right on the beach. If it's the san diego climate you like, tons of little coastal cities with a board walk or downtown but most a few degrees colder, if it's the "charm" there's a bunch of that too but it will be inland and off the beaten path (Calistoga, Healdsburg, lots of places in Sonoma or Napa county and 50 other small towns throughout Northern CA).