I went to Costa Rica past july, its beautiful and people really nice. I can give you some advices. You have to try "los rápidos" i think in english is rafting, the river its so beautiful and full of nature. You can also go to "Toruvari" is a park, where you can enjoy sports like climbing, "tiroleza" etc. Theres a lot of volcanoes but two onf the are special (arenal and poas). Means of transportation are not so good, the country is small, if you rent a car you can easily enjoy all the country. Some people organize tours, they are good, but you have to run against the time, you dont enjoy a lot, better rent a car, is cheap and easy.