The closest public that I am aware of for you would be Chattanooga MX. The owner is Daryl Lynn and he is a really good guy that cares about youth and riding, his track is wide and fast for big bikes but fast and safe for the little ones. He usually has practice on Tue. and Thurs. and hasn't had his first race yet but they are usually on Saturday.Their is Rock Crusher MX in Hiawasee GA as well as Talking Rock MX in Talking Rock between Ellijay and Jasper GA. Like Kris suggested try
www.georgiaoffroad.com it is a pretty cool website with lots of North GA'ish information and some really good people however, no where near as cool a crowd as CRF's ONLY.
Daniel