I do not believe I have seen one of their malls in PA that had any signage beyond something in tiny print buried in a long list of rules. In PA the sign does not have the force of law. If they ask me to leave and not return, there is no shortage of other places competing for my $.
It is of course trespassing to refuse to leave if asked to do so.
If I am in a state where signs do have the force of law, I pay attention to the notice requirements. Does the law specifically require a physical sign, or merely knowledge of the policy in that state?