If you're only going to be paddling one week, I'd suggest leaving the boat at home and renting from any of the many companies in Turrialba. The hassle of taking your boat is only worth it if you're going to be there for more than two or three weeks. When I went there a couple years ago, they charged a fee to bring a boat into country. Not sure if that is still the case. Another plus, if you don't take a boat, you can use public transportation to travel which is much cheaper and a very nice way to travel.
As far as places to stay, Hotel Interamericano in Turrialba (http://www.hotelinteramericano.com/
), is the place to stay This was paddler central and great place to hook up with other boaters, get info on runs, find a shuttle driver, and find rental boats.
Diego was our driver and I'm sure he's still around - he knows all the local runs and a lot of the ones that are outside of Turrialba.