Data plan in Brazil
 

I am going to visit Sao Paulo, Rio and Iguazu Falls for about two weeks. Which 3g/4g data plan do you recommend? Assume that I will use maximum 10 GB data in two weeks. Thanks.

This is defacto your only option:

http://www.tim.com.br/sp/para-voce/p...go/tim-visitor

Go to a company owned TIM store with your passport, some basic portuguese and patience for bureaucracy.

You cannot get a 'local' sim without a tax ID number (CPF). Other operators launched tourist sims around the time of the world cup, but there are many reports on the internet of difficulty getting them since.

You can indeed get and activate a sim without a CPF these days. You have to show your passport nowadays. And perhaps be a bit insistent; customer service is a non-existent concept in Brazil and few people speak English. This (showing passport, no CPF needed) was true well before the World Cup.
(Also, I believe it is now possible for any traveler to apply for a CPF at the same consulate where the visa was obtained.)

Note: If you buy a chip in Rio, this does not get you countrywide service without extra charge.
Note: Calls to numbers on the same provider are usually without charge.

This wiki seems to be reasonably up to date and complete :
http://prepaid-data-sim-card.wikia.com/wiki/Brazil

Go to a Vivo store when you land in Sao Paulo (preferably the one on Ave. Paulista near Augusta). Tell them you want internet only. You will have to go to a drug store after to put money on the SIM card. There was a strange local law enacted in some cities which prohibited the selling of SIM cards to people without verification of a local address. I find Vivo to be more tourist-friendly, overall.

SIM card experience in Rio
 

I went to a TIM store in a suburban shopping Mall. The agent spoke English and was very helpful. I asked for the Visitor SIM card and he explained that, a least for me, the better option was a normal prepaid SIM which included 200 minutes of talk, 200 text messages and 500 MG of data for a week. Longer terms with higher limits were also available. He said the Visitor card would be more expensive and provide poorer quality data. So for 5 Reis for the SIM and 5 Reis for the service (less than $3 total) I was set for the week.

Is there a store that sells prepaid SIMs at GRU Terminal 3?

Unfortunately, there isn't a store or kiosk selling pre-paid SIMs at GRU. There *was* a Vivo store hidden on the upper floor of Terminal 2, but it's closed. The Loterica place next to the old Vivo store, only sells recharge-cards, not the SIMs themselves.

FYI: as travelers, I don't know what is possible in Brazil anymore with respect to getting a pre-paid SIM. Even with a CPF, I had some difficulty getting a SIM, and eventually had to utilize the assistance of a friend. I hope tourist SIMs come back for the Olympics, and fast.

Project Fi
 

I just returned from two weeks in the state of Alagoas in the northeast. Most of my time was spent in the city of Maceio. I went out and bought a Nexus 6P and signed up for Google Project Fi before my trip. Service was great and is $10/GB (they charge you $10/GB whether it's domestic or international). You can get a Nexus 5x for and sign up for Project Fi for $200. Can probably sell the device right after you return for near break even. I found this to be a great solution for me, probably a lot easier than dealing with Brazilian companies and the hassle of getting a sim there.

Hi, there are so many conflicting reports about which SIM cards foreigners can get and which the best companies are to deal with!
I'm going to Rio for the Olympics. I'll arrive at GIG - can anyone recommend a place I can get a SIM at the airport, preferably with a data plan?
I need a phone number immediately (to call my landlord and arrange to meet), so I only really need a SIM card - the data plan can wait until the next day if necessary.
If you also know a good place in the city, that would be helpful.
I'll also be spending a few days in Manaus so nationwide 3/4G coverage would be great.
Thanks

I must say I'm shocked by your post. I have read many reports saying that in recent years it is indeed possible for foreigners to buy local SIM cards without a CPF - are you sure of your facts?

He is incorrect.

Just got back from Brazil 2 days ago.

My past few trips I had been content with my free 2G from T-Mobile, but this time I got a bit fed-up with it and Tim has a new prepaid deal. R$10 gets you 500MB and 100 Minutes for a week.

I actually ended up getting 2 Sims, because I accidentally separated the nano out from the micro and it was acting up.

Both were standard sims like you would find at a banca/quiosque, Lojas Americanas, etc. and not some tourist special.

First one I took to a TIM store to activate with passport.

It took a little while for the activation to process, and when attempting to make a call before it was active, I was directed to the set-up prompt, which had an option in English to activate with Passport number + Address in Brazil, so taking a trip to a Tim store might not even be necessary.

On the second one, I just used an online CPF generator and that worked out. This is a gray area, so use at your own risk.

*edit* also picked up an extra sim to have ready to activate whenever I return. Nobody ever asked for any ID on any of the 3 occasions when buying them, so I don't think that should be an issue.