Less than 5 hours, but it depends on which company you will fly! Maybe you can choose for a agency to book that for you, well when i travel i always use this one:
They book everything you want fly tickets, tours, Hotels... is really a nice option.
In fact, the time flight from Atlanta, Geogia to Sao Paulo or rio, Brazil takes aproximatelly 10h30 hours. To book hotels, could be a good choice www.hotels.com.