Actually any of the big hotels downtown i.e. the Hilton, Hyatt, or Marriot are in a great location to experience the city and a very short distance to the GA Dome (if that's where you're going to watch the game). As is the case in any city you'll want to use caution at night, but you should be fine walking around along Peachtree Street..there are so many great restaurants, shops, and bars within walking distance and it's a short cab ride up to Midtown or Buckhead, where there are even MORE shops, restaurants, attractions, etc.

I would definitely recommend staying downtown, I think you'll have a great time. And have fun at the football game!