I would think you would have to be incredibly careful with this one. Even if it isn't damaging to the property, most municipalities would consider this vandalism and even if it isn't, they would try to find a way to stick something to you for gluing a sign to a bank window.
Still, the example with the speedtrap seems fun, lol. I think I'll do that one.

I like that speed trap idea as well...good one!

Post it and leave... Don't leave your address on the bottom of it ^.^