Hi Andrea,
The MACC (Metro Atlanta Cycling Club) has a great ride for beginners the first Saturday every month at the Silver Comet Trail that starts at the Depot.
These guys were great in observing proper riding etiquette on the trails as so many riders zoom by and you have to compete with pedestrians for the same path. I've started training at Stone Mtn park and am slowly working up my laps to 2 1/2. I'm too twitchy to be on the local roads right now.

The Sorella team is also pretty good if you're able to hang with them.