Actually San Diego might be as good an option and easier to reach than Hawaii. We get a lot of Arizona heat refugees in August.. Disneyland, etc are nearby in the O/C... Water is never really bathwater but August is also good month for seeing Blue Whales off the coast.

I agree that San Diego would be a good choice as lots to see and do including the Midway, Balboa Park, the zoo, Coronado to see the Del Coronado Hotel where Some Like It Hot was filmed, SeaWorld if of interest and even take in a Padres game.