See the Sao Paulo Cafe website.
I ate here for breakfast because it is the only place in the Rio where breakfast is served after 11am. I had the tall stack of pancakes for $8. It was a stack of six large pancakes that were fairly tasty. There weren't many items on the breakfast menu, but it covered the main bases: eggs, pancakes, waffles, fruit, and oatmeal. They also served Starbucks drinks.
Overall, this place isn't anything special, and I am sure there are better breakfasts elsewhere in Vegas, although I thought this was tastier and a better value than the Rio breakfast buffet I had had the morning before. The decor is very bland and reminiscent of a mom’n’pop restaurant. If you are staying at the Rio, Sao Paulo Cafe isn't a bad breakfast choice, but you can do better at a different hotel.
The restaurant was a bit hard to find; follow signs closely - it’s sorta behind the Rio Box Office and Samba Theater. Worth noting: Some signs in the hotel say this place is open 24 hours, and two other signs gave different times, like 10pm and 4pm. The employees I asked didn't know either, so who knows!?