Best hotspots around Metro Atlanta with good parking, good food nearby and relatively safe:
Austell, GA: Junction of NS Georgia and Alabama Divisions - heavy freight traffic plus Amtrak's Crescent. Burger King right there and Wallace's Barbeque 1/2 mile west on US 78
Union City, GA: CSX former A&WP and ACL lines within a stone's throw of each other. Moderate to heavy freight traffic. Plenty of fast food nearby on Roosevelt Hwy/US 29 and GA Hwy 138/Shannon Mall area
Stockbridge, GA: NS former Southern Mainline to Macon - heavy freight traffic. Plenty of fast food nearby on GA Hwy 138. Highly recommend Capt Billy's Seafood Buffet right by tracks
Norcross to Buford, GA: NS former Southern Mainline to D.C. - moderate to heavy freight traffic plus Amtrak's Crescent. Highly recommend Norcross Depot Restaurant and plenty of fast food available either side of tracks up & down Buford Hwy/US 29 and west to Peachtree Ind Blvd and east to I-85
Cartersville, GA: Junction of CSX' former W&A/NC&StL/L&N line to Chattanooga and K&A/L&N line to Knoxville - heavy freight traffic and lots of fast food nearby.
There are other areas around Atlanta with light to moderate freight traffic, but those above will give you the best experience, especially if you're by yourself. I strongly recommend against railfanning inside the I-285 perimeter or in Downtown Atlanta by yourself. There are some heavy traffic areas there, but you really should have a local railfan with you to keep you from getting lost and keep you in a locked moving vehicle in some of the rougher areas.
Enjoy your visit and let me know if I can be of further assistance.
Richard E. "Rick" Shivik
HO D&H Champlain Division
Piedmont Division NMRA
Conyers,GA