Major point -- Laws vary by state. Know the laws of your state. I try not to visit establishments with these signs but occasionally have to do so. I try to honor their wishes since I'm on their property. Occasionally, there will be a business that will post a sign that does not grab my attention (no specific size requirement in my state). I patronized a bank for at least a couple of years until I noticed a "no guns" sign about three inches from the bottom of the glass entry door. I'm sure glad Kentucky just allows the owner/manager to bar access to the premises, rather than turning them into automatic criminals.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.