What prepaid cell phone can I buy in usa that i can use the minutes in brazil?

Answer 1

If you buy a GSM phone, then you can use it anywhere, provided your handset supports several frequencies.

However, the minutes will be expensive when roaming down there. If you are planning on using it more than a few minutes, it would be cheaper to buy an unlocked phone in the US and put a Brazilian prepaid SIM in it when you are there or buy a cheap prepay phone when you get there.