I would avoid HStern. The "free tour" is really just a captive sales pitch, and its hard to leave it. The jewelry seems high quality, but there are no bargains. I found much better prices back home.

I would try to find an English driver and get a tour for half a day. This can be very economical. Ours showed us an overlook 2/3rd of the way to Corcovado with an even better view of Sugar Loaf and the bay.