I am from the Bay Area. "The City" aka SF is one of the most beautiful cities on the planet and everyone should visit at least once. But if you do, DON"T call it the "Ya Area" (LMAO - Don't know what you were smokin Wolfie, but I've never even heard that one!) And FOR GOD'S SAKE DON"T call it "Frisco"!! That's a sin, and maybe even a mortal one! (But thanks for the good laugh.)
But be warned--it is NOT hot or even particularly warm in SF in the summer. In fact in the summer its downright COLD until you drive a half an hour in any direction. Unless that direction is straight toward the coast--the "beaches" in SF are more frigid than a Victorian schoolmarm. Brrrrr!!! Stinson Beach about 20 miles north is a better choice. Locals tend to skip the beach and head inland to the Delta or one of the (many) lakes, but you gotta have a boat for that unless you go to Tahoe. (My home away from home!)
Santa Cruz is a cool place to hang out for about a day, but I've never considered a vacation there. Kinda quiet. The Boardwalk was mentioned--again, good for a day visit if ya want. Windy, though. The best beach towns are definately in Southern Cal.
Overall, CA is a HUGE state with a thousand kickass choices of where to go. It just depends on how long you are going to be there, what you want to do, and whether you are travelling solo or with a favorite other
Have fun!
~~Casey