Lapa - a tiny, funky little neighborhood once known as the Montmartre of the Tropics - has in recent years developed a very active nightlife scene that i recommend. One of the most unusual but brilliant nights out I've had. It's basically a little neighbourhood where you can come and go from various houses to watch and dance to live samba bands. People fill the surrounding streets selling all sorts of shots wrapped in plastic, like little alcoholic water balloons. When we went on a Friday night, it seemed like all of Rio was there. It seemed pretty safe. Despite lots of staring at my white legs, i never felt threatened.
Lapa is dead easy to find. It's centered at the Largo da Lapa at the foot an old and very picturesque aqueduct known as the Arcos da Lapa. In addition to those two sights, Lapa offers some lovely old colonial buildings.
Is this your business?