I've lived all my life in medium-sized cities (50,000-100,000 inhabitants), so my experience may not apply to the big cities that foreigners are usually interested in, like Rio and São Paulo (with several million inhabitants each).

Of course, it's not a rich country, so there are always poor neighborhoods and bad infraestructure in some parts of the city, like bad public ilumination or dirt streets. But in overall, it's not terrible. I lived 20 years close to a neighborhood considered bad, and never got robbed - most of the violence occur because of drugs, if you stay away from their business, they won't bother you.

Public transportation is bad, but in medium/small cities everything is close and you can go to most places walking or with a bike. Healthcare is a big issue (way worse than security, in my opinion), and hospitals suffer with the lack of doctors and equipment. Cost of living is really cheap when compared to those of big cities and other countries, and you can live confortably with $1,000 (~R$ 3,500) per month.