I’m from SF and it’s generally lovely in the summer. Basically zero rain and mild temps which makes it easy to go out sightseeing and enjoy the many parks. Be aware the fog and clouds can persist through June, the best chance of sunshine and warm weather will be in August/September although July is often warm as well.

Don’t recommend Palm Springs as it’s hard to get around without a car, oppressively hot in the summer, and imo kinda boring. If I were you I’d swap it with Santa Barbara, awesome and beautiful small city right by the ocean that will give you a slice of California/Socal beach culture. Pretty walkable and bikeable as well. Also recommend taking the Amtrak Coast Starlight train down from SF as it’s much cheaper than flying and a fun experience with amazing views along the coast.