Carrying Weapons in an Unauthorized Location. Georgia Code 16-11-127
From: GeorgiaPacking.org's Places Where Firearm Carry is Off-Limits
No Signage Laws
A "No Firearms" sign on a private business does not mean anything. If your firearm is noticed, they simply ask you to leave. If the police arrive and you still refuse to leave you can be charged with criminal trespass. You keep your permit even if convicted.
However, some "public gatherings" (and any of the above areas off-limits) such as a county hospital or the post office may have signs posted to inform you they are off-limits. You probably will lose your permit for several years if convicted.
So, just because you see a sign does not mean it is or isn't off-limits and just because you don't see a sign does not mean it is or isn't off-limits.