You can't ever say "there's nothing to do" in Southern California. Even if you do, people will just laugh at you. Forget those expensive Halloween club party's in Hollywood, support the locals and have a good time!
and then on Saturday
Meet at 5:30 PM
Again... meet at 5:30 PM
and ALL weekend long really, CARNEVIL at the Gasser Lounge every night
and jump ahead to Wednesday ...
Here's a LINK to the L.A. Tourist listing of Halloween Events this weekend (and surrounding dates) if you're looking to go full out.