I don't believe there are any Apple Stores in Brazil or any other Latin American country, but if you go to the nearest Apple service center, they will still do warranty repairs and exchanges, even if the device was originally bought in another country, or if you need help when traveling away from home. It might help to make things go easier if you have your original receipt, and if you've registered the device for warranty. In general, Apple is very progressive when it comes to customer service. I've heard all sorts of great first-hand stories about Apple staff and service centers going out of their way to help foreign travelers.