yes, you are perfectly right, sao paulo is the business capital of Brazil, so it's a good choice to go there.
As far as I know, only the EMBA of University of Sao Paulo is taught in English as well, but all the regular MBA programs are only on Portuguese.
Here is a link with the MBA programs you can do in Brazil:
http://www.find-mba.com/brazil/1You will always find there a link to the website of each program, so can do a research, as well looking for the information on instruction language.
The University of Sao Paulo has a wide choice of different MBA courses, as I said, maybe you'll find something in English? If not, may I ask you if you speak Spanish? Because in that case it will be quite easy for you to learn Portuguese and study in Portuguese.