I have been studying Spanish for a couple of years. Last year I went backpacking and took lessons in Spain. Next year I'm going to Nicaragua.
After exhaustive research I've decided to stay in La Mariposa for a month next May. Reasons:
1) Great reviews on various web sites including the Trip Adviser
2) One-stop-shop - A family-feel hotel (only 8 rooms with private bathroom) providing 3 meals a day (mostly vegetarian); one-on-one Spanish lessons in the morning and field trips in the afternoon and day trips in the weekends; all hotel staff help students practice Spanish outside classes; all these for only US$300 per week or US$1,000 for 4 weeks;
3) Admirable course - this is an eco-hotel growing their own organic farm; the revenue of the business provides employment to locals; the hotel supports other community projects including an elementary school; the hotel is powered by solar energy.
4) The owner - Paulette, an admirable lady, sold her house in UK a couple of years ago and moved here in pursuit of her dream - contributing in the sustainable development of Nicaragua; I've only read about her, emailed her a few times making booking for next May, can't wait to meet her in person;
5) Immersion - the activities are designed to help students see the real Nicaragua.
I'm so looking forward to this trip.
This is the hotel web site
http://mariposaspanishschool.com/index.html