Did you consider Copan Ruinas in Honduras? There is Ixbalanque
http://ixbalanque.com/ or Guacamaya
http://guacamaya.com/ - both are good quality, with excellent teachers and a friendly atmosphere. You also can take part in activities with other students. For both, you can stay with a local family which keeps the price down. Or, there are several good options for hotels in the little town. The price of a room is cheap. Copan is a tranquil place and there are some ancient ruins on the edge of the town which are amazing.