Yeah, I would have done that slightly differently - in June, you can go from LA-SF on Highway 1, then cut across through Yosemite and the White Mountains (bristlecone pines!) to Las Vegas, then come back down through Palm Springs to San Diego, and end up back in LA. Your itinerary's fine, though.
LA's going to be a bit hot and miserable in summer, so you'll want to stay close to the beach - Santa Monica, Venice Beach, all these are good options. In Las Vegas it's going to be stinking hot (you're in the desert in the height of summer), so plan to spend a lot of time by the pool, or indoors (go see Penn and Teller at the Rio, and maybe whoever's in residence at Caesars).
SF's going to be much cooler and foggier - you'll probably appreciate the change. Rent a bike and go riding around the city - if you're reasonably fit you can even ride all the way across the Golden Gate Bridge to Sausalito, the next town up the road from SF, and then catch a ferry back. Go see the museums - the Cal Academy of Science is terrific, and the just-reopened SF MOMA is the equal of any modern art museum in the world.
And nobody really does this, but you should: if you're interested in the cable cars, make sure you stop by the Cable Car Museum, just up near North Beach; you can see the huge drive wheels that power the cables, and even buy a little slice of cable as a souvenir paperweight.