My wife and I spent New Year's Eve in Rio many years ago at a time when we lived in Miami and that was our usual New Year's experience. I remember being impressed at how organized things were that night - even more so than back in the USA. We were very careful the other nights to not wander on the beach after dark, and in general have always been very conscious of surroundings during Brazil visits over the years. But on New Year's Eve we felt comfortable walking around Copacabana and the beach in areas with a lot of people and made sure not to have anything valuable with us.