I'd be annoyed with the friends for not telling you, and I like the idea of your going to SF, should you be able to catch a plane in a short time.
Alternately, I've been to Vegas, which is also not a big draw for me, with a group of girlfriends for one's birthday, did not gamble (not my thing) and enjoyed being with the friends. On the other hand, they didn't fool me first.
Next alternative - I take it you are in the LA area? Drive yourself to someplace wonderful that is closer and check it out. There is much to see between LA/SF, though I wouldn't claim that for highway 5.
Are you new to California?