1'st method
Run vimtutor (from command line) with 2 letter language code like:
vimtutor en (for english)
vimtutor pt (for portuguese)
etc...
2'nd method
Open tutor with different language with:
vim /usr/share/vim/vim74/tutor/tutor (for english)
vim /usr/share/vim/vim74/tutor/tutor.pt (for portuguese)
etc...
(The same default path applies to Cygwin on Windows. You may want to change vim74 part if you have different version)
Using this method you may actually want to copy the file somewhere else first and then open the copy, because you are going to modify it.
3'rd method
Vimtutor opens in Portuguese by default because you probably have some environmental variable set to Portugese like: LC_ALL, LANG, LANGUAGE (check it with env | grep -P 'LC_ALL|LANG'. You may want to change it like this:
export LC_ALL=en_US.utf8
and then run vimtutor.