Some tips

When I was planning to do my exchange, I was very concerned about what its necessary when you are going to Brazil..

-First of all you need to take classes of Portuguese, seems easy.. but when they talk, they talk so fast!
-To have all vaccinations, the ones you need in Mexico and yellow fever (15 days before the flight)
-International insurance
-Here are the requirements for the student visa (which here is very important, even if they have free access for 120 days.

-This is the official link of the consulado-geral do brasil
http://cgmexico.itamaraty.gov.br/pt-br/visa_de_estudiante_%28vitem-iv%29.xml

-Also to bring some credit cards and debit cards (HSBC or Santander). In these days I have problems with the debit cards (Santander) because the cashiers machines are not connected with the Mexican banks.  So its better if you can bring from different banks, i didn't have any problem with the credit cards (they saved my life).

-Some cash its also necessary.. its difficult to find reals in Mexico, so I recommend to bring dollars and exchange for reals in the airport

-People here are very friendly and when you are having trouble to communicate always its better to speak spanish  (they don't like English)

I think those are the tips that I wish someone had told me before coming