I have not spent much time taking city shots of Atlanta, but hope to sometime in August once I am back home from school. I would suggest that you be careful around the campus of Georgia Tech (near the Varsity & MARTA station area also). While you shouldn't have a problem that is a bit more dodgy than others from my experiences. You might want to think about getting over to Lenox area I know there are a few views of that skyline by a river, but once again I cant give you directions (only seen the shots). Make sure you post them, love to see your shots when you return!
PS: if you got time you should come to my suburb (Roswell) and hit up the Roswell Mill at Vickery Creek. I got a few shots of the waterfall on my webpage. Its a cool place to visit if you got the free time. Its about 20-30 minutes from downtown depending on where exactly you are staying (maybe longer if your really south).