I just returned from two weeks in the state of Alagoas in the northeast. Most of my time was spent in the city of Maceio. I went out and bought a Nexus 6P and signed up for Google Project Fi before my trip. Service was great and is $10/GB (they charge you $10/GB whether it's domestic or international). You can get a Nexus 5x for and sign up for Project Fi for $200. Can probably sell the device right after you return for near break even. I found this to be a great solution for me, probably a lot easier than dealing with Brazilian companies and the hassle of getting a sim there.