Don't go to Universal Studios. There is NOTHING to do and it isn't worth the money. CityWalk (the big outdoor mall on the property) is kinda cool though..
The only thing the Valley has going on is if you are really big into the history of the film industry, that is where almost all the studios are (except for CBS and Paramount, really). Warner Brothers regularly holds tour, as I think NBC does. Disney is a bit more secretive of their shit and I don't think they do many tours. Also, if I were you I would go see Conan O'Brien or Jay Leno or whoever you enjoy. Also in Burbank there is the original Bob's Big Boy. Go there on a Friday night to see crazy old farts with their tricked out cars
PS, Go to Six Flags or Disneyland. Disneyland doesn't have many 'exciting' rides, but it's something everyone should experience at least once in their life.
PPS, Hike to the Hollywood sign -- don't drive. It makes it more of an adventure.. Plus you'll be able to see it from a few yards away as opposed to about 1000 feet..