Retsio is right. I know you probably tried to save money by flying Southwest, but the Atlanta airport is all about Delta. Despite that, the inside transport system here is unsurpassed by any other airport I have been to, and I have travelled most places in the world. Therefore, as others stated, your issue will be getting to and from Alpharetta from the airport, but if you have an airport shuttle (which is hard to believe this is offered by an Alpharetta hotel BTW), you'll leave the traffic issues to the drivers. Just allow extra time on Friday, but remember Atlanta car traffic can be bad any time based on accidents and road construction delays.