Turn on International Roaming on your phone. You get automatic coverage in 140+ countries. I believe this feature is added to ALL Simple Choice plans, new and old.
Your data speed will be slow but it will work for small lookups. If you need a lot of high speed data, I recommend buying a data sim locally or adding a data bucket to your account (expensive!)
Brazil is one of the covered countries. Data is good enough to use Google Maps for hours of driving. Streaming radio newscasts works more than half the time. Email works 100%. You will not have the FAST speed you have in the U.S. so you can't watch video.
There is no real need to upgrade - but TM will sell you a bundle of fast data. You would be better off trying the free data first. As mentioned by user above - in that case get TM to SIM unlock the phone and get a local SIM.