The value tebow adds is to some A ball affiliate in Florida who wants to sell some tickets. There's no MLB reason to sign him. Just sign him to put him in A ball and get a couple thousand extra bucks to the game.
As outlined in the article, the Braves own the GCL, Danville, Mississippi, and Gwinnett teams. So I imagine they'd start him in rookie ball, send him to A but then hope to get him to AA as quickly as possible.