In the past I always activated Sim cards with my passport number... if you've got a CPF, more straightforward. Or just ask a mate to register it with theirs

Will you be making many voice calls? If so, the network that other people use may determine what you buy, as it is incredibly expensive to call other networks.

I got the impression Tim was dominating in Brazil, but perhaps that's not the case

Can anyone recommend a data plan that doesn't suck? With Tim, 50 cents per day gets you 10mb of data, then it slows down to a snails pace. With Vivo, you pay 10 reais a month and get 200mb (?!). Do Oi or Claro offer anything better?