Boa noite Zairina!
How lovely! Just think this time next week you'll be lounging on gorgeous beaches, along with a sea of humanity from the four corners, all taking in the splendor that is Rio. Of course the real beauty is that while you may be solo, you're never truly alone with the spirited and sociable Cariocas all around you.
I personally think apartments are better, particularly if the price is reasonable. Having said that, I agree there is an added benefit to socializing amongst your peers while on holiday. Perhaps one of the many social-networking sites may be of benefit to you, as you can reach out to similarly-situated travelers before you arrive.
Our resident Carioca and Rio DE Gabi recommends this site -
www.couchsurfing.com
Travel safe, have too much fun - and save a little sol for a FlyGuy who'll lands in 17 dias... :-)
Welcome to Paradise!
www.ipanema.com
www.lanalapa.com.br