Check out georgiaoffroad.com for a listing of tracks and legal ORV trails to ride. Living in Kennesaw I don't think you're too far from the mountains. The trails in Dahlonega are nice, as are the ones in the Toccoa area at Locust Stake, all the way up in the far northeast corner of Georgia, near Clayton.
Please ride responsibly, to make up for the misuse of the trails by beer-guzzling, no-helmet wearing, passenger-carrying rednecks on four-wheelers that lack the skill/sobriety to operate something with four wheels, much less two.