I've been riding offroad in north GA for the last 30+ years. I am not currently aware of ANY singletrack trails, that exist on public land, except in the ORV areas. I've been told by 2 different rangers that unless a trail is specifically marked OK for motorized travel it is open only to foot travel. The penalties for riding a motorcycle or ATV on a trail that is not specifically posted for motorized travel is a steep fine and seizure of your motorcycle. I'm not trying to rain on your parade here. Just relaying first hand information I've gathered from my many trips through the public lands of north GA.
There are special events throughout the year that get special permission to ride trails that are otherwise closed to motorcycles. The annual dualsport event sponsored by GARTRA (http://gartra.net
) is one such example.
Forest service roads are numerous in the area and are open to street legal motorcycles unless posted otherwise.