I saw this sign and a link to the creator's site, author Chuck Klein, in the Gunbroker newsletter. He's given full permission to anyone who wants to post their business premises with it.
I'll spend more time and money in a business where the proprietors care enough about public safety to post such signs. All sorts of gun-free zones come to mind, places where murderers and robbers don't check their guns at the door, where the blood of innocents has pooled. There are schools, churches, courthouses, malls, government facilities and murder capitals such as Detroit, Chicago, and the District of Columbia where law-abiding citizens struggling to survive are treated like potential criminals.
When I see a gun-ban sign, I have to decide to go back to the parking lot and lock my pistol in the car before entry, to disobey the sign or to spend money elsewhere. Criminals on the other hand, make other decisions. They've chosen to commit armed robbery, to rape or to kill people who most likely have no means to resist. They sure aren't going to pause at the sight of a gun-ban sign. In fact, it should raise their hopes.
On the other hand, it must be disappointing for them when they expect a victim-rich environment but encounter armed people determined to live. So the places with gun-ban signs must be owned by people who seek to extend every courtesy to violent felons.