Unless the law in PA gives legal weight to such signs, the only thing that can be done (should the management see your concealed firearm (huh???), would be to ask you to leave. Failure to leave when asked may result in trespass charges.
If you enter such a place and don't leave when ask you may be charged with trespass. If you enter suh a place that you know posted. You may be charged with defiant trespass, a more serious offense.
A good place to look for information on PA gun laws is pafoa.org.