You can buy a SIM card for about 86.83 BRL, which includes 1 GB of data plan. You can choose from 7 telecoms: Algar Telecom, Claro, Nextel, Oi, Sercomtel, TIM or Vivo.
Brazil uses GSM mobile networks GSM 850, GSM 900, GSM 1800 and GSM 1900.
If you don't want to buy SIM card in Brazil upon arrival, make sure to check the roaming charges with your telecom provider before your departure so there are no surprises when you return home.