The trail system is very new and fairly limited, but for a compact area it does offer a nice introduction to the varying degrees of mountain biking difficulty. This is an excellent location for beginners and children but will not satisfy the mtb enthusiast.
From downtown Atlanta take I-75 North to exit 261 (Delk Road). Go West for about a half mile and you will cross over Cobb Pkwy/Hwy 41 and the road becomes South Cobb Drive. A.L. Burruss Park is the first entrance on your right once you cross over Cobb Pkwy.
http://www.singletracks.com/item.php?c=1&i=4160