As Brazil is a huge country the pronunciation can vary slightly from region to region, but in general you will not have problems understanding regional accents.
For the letters R/S/X/Z there are two major regional differences in pronunciation between São Paulo and Rio de Janeiro. Both pronunciations are correct.
Be aware of this difference. Learn to distinguish between them and choose the easiest one for you.
Remark: You can find more about different regional pronunciations in my Portuguese Grammar book.