Leblon is considered the best area of Rio. There are few hotels and usually very few tourist. If you have been in Rio, you probably know the familiar sights of Copacabana with tons of "predator" girls (usually black) looking for that white male tourist. It's a mutual thing and if you are just looking to pay for sex, stay there!
But if you are looking for normal Brasilian people, and I am speaking also to the ladies that are reading me now, Leblon is the best place. During the day, there is a constant stream of people walking here, with very few of the above mentioned categories. The hot spot in daylight is certainly the Post Office Square. Night hot spot is the Pizzeria Guanabara. Very safe to walk, but again, do not wear your gold doorknob-size pendant. Just common sense. :-)