Great Experience

Vase is the best option if you are looking for something in south America, the have a lot of programs from schools to working in the jungle.
The best thing is that you get to live with people from another countries and learn a lot of this beautiful culture. Is a small country but it has a lot of biodiversity.
You should definetely go to all the beaches, specially montañita. Try to visit a lot of places while you are there.
Do not forget Galapagos that is the most amazing thing, you can swim with sharks.