Regardless of the validity of the signage, keep in mind, if carrying past invalid signs, one should be very familiar with the trespass laws of the jurisdiction. In general, in the USA, the owner of private property, or his designee, can eject just about anyone for any reason. Failure to immediately leave when asked/told do so, can get one into trouble for trespassing. Sue the establishment later, if justified, but get out when asked/told. Protest from outside the property boundary.
The above is not legal advice, but is practical advice.