Well, brandishing is a bad grey area to some. I've been told and warned that just displaying a firearm can lead to lawsuits at times, but rarely would lead to criminal prosecution. As for "putting your hand on it" when approaching a would be car thief, that could be touchy in some cities. Personally I think I'd be likely to do whatever I wanted if the car were in my front driveway, but less likely if it were parked at the mall or such.

As for carrying it, like you said, if they don't screen for weapons and it isn't prohibited specifically by law, then the sign means nothing. Karl.