I'm lucky to have a park across the street from me where I fly my helis and smaller foamies. They love us there and the rangers come over to watch. The soccer fields where I like to fly the bigger stuff there is a huge sign that says "no unauthorized usage". It took me for ever to get a hold of the right people but I finally got permission. Like Vic said using common sense goes along way as I told them I would never fly if kids, soccer players were present. Heck it's vacant 90% of the time.