Do "Enter At Own Risk" signs have the same standing in the USA as the do here? Probably not.
From what I am to understand, in Australia an "enter at own risk" sign means exactly that, if you see the sign, chose to enter and get hurt, the homeowner is covered because you done it on your own accord after being notified that it is risky to do so. If that applies in the US then its time to post some signs and set up some boobie traps.
The reason I ask is because one of my friends mums got away with her dog biting someone (meaning, the dog didn't get put down) because they'd jumped her fence one night and the dog attacked one of them, all thanks to the "enter at own risk" sign... But the US may be different.