Not familiar with that place, or the sign. Is it posted on the entrances to the building? This one looks to be in a display case, in which case, I'd take it to mean no guns are present in the display case. Which is clear from the picture, there are indeed no guns in the display case.
It is not conspicuously posted at the entrance to the property, which is what would be required of someone who's already got a contract with the lodge for the room. The contract turns it into a "civil matter", and any cop who attempts to interfere would be engaging in the tort of "intentional interference with economic relations". For someone who simply wandered in, with no contract, then remaining on the property after having been notified to get out would be a trespasser, subject to defenses of the sign's being inconspicuous, ambiguous, and not communicating anything other than the lack of firearms in the case.
Do they have "terms and conditions" you have to sign up to in order to reserve a room that include a no-firearms provision?