I've never done anything in a public place other than a tiny threshold dose of MDMA... granted, I've walked to a park by the river multiple times while tripping on LSD, but that was only part of the trip. I've never experienced an entire trip in a public domain, much less a lively thing like a festival or rave.
Also, @tweaky, we're trying to find some stuff, but our connect hasn't been answering our calls for a while. (Even when we're just trying to get a hold of him to hang out and stuff - we're casual friends and all.) Makes me sad.
I wish I could find out where people got their stuff directly, so that I didn't have to work through a middle-man.