SF: Haight, the stretch of Haight St. from Golden Gate Park on east has nice shops and is good to take a walk. The Presidio. Golden Gate Bridge. I strongly recommend taking a boat ride around the bay. You should be able to find tickets around the wharves (Fisherman's Wharf, etc.). I really liked Chinatown and the City Lights bookstore, near each other. People will tell you to stay away from Fisherman's Wharf, Pier 39 and Alcatraz because they are tourist traps. Ignore them. Their locations have stunning views of the bay.
LA: Hollywood Blvd. between Highland and Vine is a great place for a walk. The Grove (a.k.a. the original Farmer's Market) is a personal favorite of mine, but not the new mall portion. Universal Citywalk has the Hard Rock Cafe, and Universal Studios theme park and backlot nearby. It's a tourist trap that's completely artificial, but that doesn't matter because it's so much fun there. Long Beach is very pretty, IMO. Santa Monica is very popular, and it has beach, too. I personally like the Grand Central Market and wholesale shops in downtown during the daytime, but that's not for everyone.
Las Vegas: The Strip and Fremont Street Experience are where it's at. Check out all the big casinos, if that's your thing. Stuff is somewhat cheaper at Fremont St.
