Someone put up No Trespassing signs on a gravel bar at my local creek, and I was like "oh no you don't!" So I called the county prosecutor (we know each other) and explained my concerns. He said, just stay in the water, and if by chance a deputy shows up and wants to write me a ticket....just BE NICE, take the ticket, and he'd throw it out when it crossed his desk. I stayed in the water and never had any problems. Several just ignored the signs and fished from the gravel bar. They didn't have any problems either.
What needs to be addressed by agents is people putting up signs and purple paint in places that they don't actually own. In the Trespassing case that I plead guilty to I know who called the law....and I also know that he can't prove that he owns the property. He took it by adverse possession, doesn't pay taxes on it, and has no deed. I could have easily beat it, but they wouldn't allow me to represent myself. Had to have an attorney....which is also BS.