Legal or not, the sign says they don't want guns. Their wings ain't good enough for me to either; ignore the sign & carry anyway(which I wouldn't do as I do believe a property owners rights out weigh mine on their property after all no one makes me go there), or disarm before entering.
When I see the "ignore it" comments , it kinda irks me. Who is forcing you to go where you (or your gun) is not wanted? You want others to respect your rights but refuse to respect theirs? Kinda hypocritical in my book. See a sign, go somewhere else without a sign, legal or correct or not, the owner has made their wishes known. They don't want guns, therefore they must not want gun carriers or their money.
Posted from the outer reaches of the universe via my Star Fleet communicator! Live long & prosper.