If you take a look at the web site for the event highlight,
http://www.bodyartexpo.com/HIGHLIGHTS.PHP , you can see that they are going to have all sorts of stuff.
There can't be genital nudity, it being a public place, but you will see a lot of skin, most of it heavily tattooed. You have a good chance of seeing as diverse a group as with any Bay Area event. Just because the guy standing next to you is covered head-to-toe in tattoos doesn't mean he might not still be a banker, lawyer or doctor. Oh, and the huge guys covered in tattoos who look like they belong to a biker gang most often are just that.
Actually, the crowd photos on the site do give a good idea of what the event will most likely look like.
Wear comfortable shoes. As with all conventions, there's never enough places to sit down. hahahaha