Not a business but a public place where I saw a "no weapons" sign. It was a Charleston school building being used as a shelter for Hurricane Matthew evacuees. It wasn't a "legal" sign, at least according to SC's definition for "no gun" signage. Since the building was a school campus I suppose it was off limits for guns anyway, even though it wasn't being used as a school at the time.
If you (anyone) needed to stay in a storm shelter, would you carry, leave your gun at home or in your car, or what? Just curious.