Just call ahead to UOP. They're usually pretty good about setting something up and finding someone to show you around. If they can't find anyone, give me a PM and I'll try show you around as best as I can.
My experience with UCSF was that it was a little harder to just walk in and get someone to show you around. It'll help if you know someone there already. When I went, I had a 4th year I knew from high school take me on a tour.