I too have just returned from a weeks holiday in RIO. It was great! I saw no evidence at all of the crime I had read about and was wary of. The Brazilian people I saw in Copacabana (where I stayed at a great apartment), Ipanema, Leblon, Leme, downtown, Botofago, Gloria, Santa Theresa, etc., etc. were a happy, wonderful lot. The Diners Club van will let you off in the centre of Copacabana at the Rio Othon Palace. It isn't very close to the Sheraton, which is closer to Leblon, but the Sheraton itself has a shuttle that offers service to most parts of RIO. Perhaps you can arrange, (or find the schedule) to have it pick you up from where the Diners van lets you off.
The Sheraton is a lovely property, but it is a little too far off the beaten track for my taste. I love Copacabana. The water was warm, the beaches much less crowded and I now know a new definition for the word "dental floss".
Booze is dirt cheap in Brazil. It costs less than a loaf of bread in many instances. Do try a caipirinha. It's great. And don't forget the cafezinho (coffee). It's almost as potent.
The buses are easy to decipher. Destinations are displayed on the front. They are driven fast, often and with little regard for the cars around them. They are a blast, and at 0.85 R, can get you to Sugarloaf, Corcovada or anywhere you want to go. You're not at the mercy of a taxi driver and his creative routings.
Have fun, and if you want some more info, please e-mail.