I was in the EVOLC (formerly known as CREST) program in 2009, as one of the first volunteers. The program gave us a 2-week training period, which was quite useful, and then we were placed in our respective locations. I moved to the rural town of Uvita, in the South Pacific. Transportation was ok, but I bought a scooter to be able to go to the beach without waiting for the bus once every 2 hours. The people were very friendly - and I still have friends I can visit!
The culture is PURA VIDA, which translates to LIFE IS GOOD. If you don't mind the humidity and enjoy a tropical climate, then this is the place for you!
Self-starters need apply, because you will most likely be the first in a community that has not had a teacher before. This means you are in charge of the curriculum, hours, materials, and placing your students in the correct levels. Shy people need not apply!
What you put into this program, you will get out of it. I taught 20 hours a week, with about 10 hours of work on preparation. It was "English by Kelly" and I loved it!
Be willing to learn Spanish. And don't forget your bug spray and sun lotion, and especially an open mind!
Good luck, and enjoy the ride. PURA VIDA!