Ok, ......
Yes open carry is legal in Georgia. So is concealed carry. You must have a valid license to do either or both outside of your home, car or place of business.
Inside of your home, car or place of business, there are no rules....unless of course you are a convicted felon or otherwise prohibited from carrying....
With a license, you can not carry in schools, churches, courthouses, jails, prisons, nuclear power plants and MOST government buildings. You can carry in State owned parks or county owned parks. Local governments can not pass any local laws prohibiting firearms carry.
Signs prohibiting firearms carry no legal weight in and of themselves...however, the management can REQUIRE you to either leave, or disarm, or both, and if you don't a LEO can arrest you for criminal trespass once you have been asked to do so.