I didn't do what you are doing, but I have a couple thoughts about visiting:
1) How they treat you once you're admitted is totally different from when you're just somebody in the crowd. Admissions offices usually won't do much for you besides tell you to take a tour. And Boalt's building is pretty unimpressive, so don't make your mind up about the school based on that.
2) Talk to students! If you're going during the weekend, it's going to be tough. But if you can go when students are there and meet a few, they can give you a real sense of what the school is like.
3) Even if the school doesn't let you visit a class, email a prof directly and ask permission to visit. They will usually be fine with it.
4) Search out blogs for that school. I've found a couple blogs for schools I'm thinking about that give very candid takes on a person's entire law school career. This is a good Boalt blog: http://boaltalk.blogspot.com
. This UCLA guy's blog is really great for showing what first year is like: http://www.matthewb.com/