Thank you for your reply. I guess I can go in and see if they ask me to leave. If they do, I will in fact leave."or after having been forbidden to do so by a sign or signs posted" That phrase refers to a "NO TRESPASSING" sign. Not a "NO GUNS" sign. As you well know "NO GUNS" signs have no effect of law unless the specific place is addressed in the law and then only for concealed carry. The sign is nothing more than a request.
The problem is cops don't have any understanding of trespass law, let alone gun laws.