Brazilians have a reputation for being attractive, football playing, party people ! This is true to a large extent.
All the Brazilians you will meet are generally very friendly and will help you out if you need directions, even if you can't speak each others language ! Don't be surprised if you are approached in the street this is normal.
The natives or Rio (named Cariocas) and well known for their charm, happy go lucky style and relaxed attitudes. Just don't think you are on to something when they give you their phone number and tell you to call later. It's just a common courtesy, there is nothing in it. If you arrange to meet someone arrange the first meeting close to where you are staying. The reason being they are quite likely to not turn up and not inform you of them canceling ! And they will almost certainly be late. Any arrangement made in Rio will be automatically cancelled in the event of rain.
Brazil is also much more multi cultural than it's media has actually portrayed to the world in recent times.
There have been various immigration waves to Brazil. After the original Portuguese settlers in the 1500's several million slaves were shipped to Brazil from Portugal's African Colonies of Angola and Mozambique. Italians and Germans flooded in during the 19th &20th Centuries and after the abolition of slavery in 1889 Japanese immigrants arrived en-mass in São Paulo.
Nowadays the regions of Brazil reflect these historic immigration trends. The Southern States of Santa Catarina and Rio Grande do Sul are the most ethnically European. Rio de Janeiro is perhaps the most mixed and then as you travel further north into Salvador Bahia the population becomes more African. Go into the interior and the population looks more Amerindian.
After 500 years of interracial marriage between peoples of European, African and Amerindian origins modern Brazil is very much a rainbow nation and your perception of black and white (if you have one) will be challenged.
Whilst Brazil is a mixed race country, until recently it was acceptable to have racist attitudes. Brazil had no Civil Rights movement and social exclusion of poor people and those of African, Amerindian or mixed race origin were happily accepted by the establishment. Sadly racism does still exist in present day Brazil as does a complex class system. People still make racist jokes such as "black people don't work so they live in favelas" and "money whitens". Of course if you're a famous footballer such idiocy doesn't apply.