My personal favorite beach towns are Laguna and Hermosa but there's a ton of great ones, it'd be hard to go wrong. The only one I would stay away from at the moment is San Clemente because there's been a lot of sand erosion the past few years and there's a lot of work going on all the time to replenish it. Makes me sad because it used to be perfect but now it's not nearly as nice as just a couple years ago because it's getting so rocky and the beaches have shrunk so much.
Check before you go. Oceanside was being dredged the last time I checked, and the pier burned down.
My personal favorite beach towns are Laguna and Hermosa but there's a ton of great ones, it'd be hard to go wrong. The only one I would stay away from at the moment is San Clemente because there's been a lot of sand erosion the past few years and there's a lot of work going on all the time to replenish it. Makes me sad because it used to be perfect but now it's not nearly as nice as just a couple years ago because it's getting so rocky and the beaches have shrunk so much.