São Paulo is a very large city, so have that in mind when moving around. Real slow traffic on rush hours, and if it rains it gets worse, so if at all possible plan on staying close to where you'll be working at. Also have that in mind when going out by yourself, i.e., no flashy jewelry or big camera.

I too think the credit card comment is highly exagerated. It happens here as it would happen pretty much anywhere else. Also exagerated is the comment that few employees will speak English on the hotel. Unless you're in a really crappy place most employees will speak English. Not a perfect English most times, but good enough to get by.

Arriving at GRU, unless you have someone picking you up, go straight out and look for a blue and white taxi called Guarucoop. It will be right outside the arrivals area. They take credit cards and will take you to your hotel for about R$100.

Tipping is usually 10% of your check on restaurants and bars, apart from some places that for some reason are now charging 12.5%. It usually comes on the check already, so there is no need to leave extra on the table as in US.

São Paulo has some great restaurants and museums, if you have time for that. Let me know if you need a few indications.