There are so many interesting places to visit in Rio: botanical garden, sugar loaf, corcovado, copacabana fortress, ipanema, the neighbohood of Santa Teresa, etc.
But if you have a short time I suggest you to book the services of a private tour operator: they make everything easier and safer. I used the services of a private tour called rio experience, announced here, in fodors. Enjoy Rio!

I will be there during Carnivale in 2012. Can anyone recommend a tour guide or company for a tour to Sugar Loaf.

Due to the festivities I do not want to try to use a cab etc..

I have been quoted a price of over $300 for the tour....I just have to get it cheaper than that!!!

Thanks...

The view from the Corcovado is absolutely magnificent and really is a world-class must-see. The short, steep, and winding cog railway through dense tropical forest to the top is a great ride.

My only visit to Rio was on an 11 hour layover. It gave us just enough time to visit Pao de Acucar (Sugarloaf), Corcovado and Ipanema Beach with lunch in the middle somewhere. It was pretty rushed and if you plan to come back sometime soon, I would definitely focus on one or two areas followed by dinner at Antiquarius or one of the fine cafes along the beach.

Leanna-
Why "Due to the festivities I do not want to try to use a cab etc.."? A taxi would be the cheapest and most efficient way to get to the base station of Sugarloaf and back to your accomodation. Onthe way back, you can take a bit of a stroll around the Urca neighborhood and find a taxi rank in the neighborhood. In my extensive experience, taxi drivers in Rio, some of whom I number among my friends, are honest family men just out to support their families by getting you where you want to go in the most direct manner possible. There is no need for a guide once on the mountain.

I live in Rio, and Corcovado and Sugar Loaf is a must. Don't lose it. Try to walk in a saturday afternoon in Ipanema Beach, and see the sun set... having and ice cream it is gorgeous. Unfortunately, the train in Santa Teresa had a very bad accident, and I believe it is going to take long to travel again. try the bar DEVASSA in Ipanema, at Anibal de Mendonça for a beer. Just relax and enjoy.