You have seen the great photos from Guyana, Suriname, and French Guyane (collectively called the Guianas down here), but there is a darker side to these places: the cost. They are some of the most expensive countries to visit in South America. Here is a bit more of the breakdown:
Suriname: $190/day. We covered most of this one already. Food is reasonable and cheapish accomodation can be found, but transport is really expensive to the interior. Might have been possible to get their cheaper, but we had heard some bad stories. The $100 for visas is also ridiculous, and really brings up the average since we were only there for 6 days, but they are quick to remind you that the US levies similar visa fees on them. Oh, and on the visa side, if you are getting your Suriname Visa in Georgetown, it isn't hard, but you must pay them in US dollars and they only accept newer $10, $20, and $50 bills. This is true no matter what country you are from. They absolutely will not accept local currency, their own currency, or $100 bills. We can recommend Blue Frog Travels for arranging trips to the interior. They were really great for us, though the A/C was unfortunately broke on their vehicle at the time. Jodensavanne and Brownsberg National Park are both nice places.
French Guyane: $165/day. Had it not been for the kindness of Dan the American and Manuela and Max the Italians, this would have been much, much higher. French Guyane really does cost more than France. Dan was nice enough not only to drive us half way across the country, but to take us to dinner as well. Manuela and Max were kind enough to put us up for about the price of the cheapest hotel rooms, which were all booked, and they helped us get around. Hotel rooms cost a minimum of 50 euros ($70 at present) for less than great places, though they do all have A/C. Try to find people with whom you can stay. Definitely try couch surfing here if you can lock in your dates (we couldn't). A lot of people apparently hitchhike. Consider it. If you don't speak any French (Tara does), it will be difficult. I was excited to go to Cayenne because it is the city for which Cayenne pepper is named and that seemed to give it a fun aura. It turns out that Cayenne is a boring town, especially in the summer. Go to the prison camp in St. Laurent (try to find a guide who speaks English), go to the space launch tours in Kourou (free, but in French--probably interesting even if you don't have Tara translating), and go to Glacier for ice cream in Kourou.