I'm glad I didn't suggest the 10 Reais Public Bus to Metro to Train route

The Airport Bus is perfectly safe and the drop-off point at the Hyatt is a good area but I would hop in a taxi at the Hyatt to get to the Sheraton if you have luggage not because the walk is unsafe but because the footpaths are atrocious!

If your arrival doesn't coincide with the timetable for the bus that I suggested almost as good is to take the more frequent bus run by the same company at the same price to Congonhas Airport and hop in a taxi there - its BRL20-25 to the Sheraton