Smokers of Perth

I'm inclined to think that the writer of this sign didn't know where to place the apostrophe and therefore took the coward's way out and left it out entirely. Let me help you, Bakery. There is unfortunately more than one smoker in Perth. So you can expect many smokers to come to your venue. In that case, place the apostrophe after the 's', as per the rules regarding plural possessives. Gah. Don't they teach grammar in schools anymore?

Incidentally, I think calling the courtyard a smoke free area is a bit rich anyway. Don't they know that smoke floats? It fills the courtyard!