This was great experience for me. The first month was in San Jose, where you take classes in Spanish, local history and politics during the week with educational and or recreational trips on weekends. I had a lot of fun during this period and you really get to know the 15 or so other students participating. The teachers and administrators are awesome as well.
After the first month, you go on your own for your Internship. They have loads of options in varying fields all over the country and in Nicaragua as well. I chose to work in Cobano a small village on the Nicoya Peninsula. ICADS set me up with an awesome family for my home stay. The parents were cool. I would often have late night drinking sessions with the patriarch while watching football. (Viva Saprissa!). And their children were adorable, I spent many afternoons hanging out with them around town or at the rivers or beaches near by.
My internship was actually more like two related internships. In the mornings I assisted at the CEN (Centro de Educación y Nutrición). Essentially a day care, I helped wrangle a bunch of unruly 3-5 year olds and made sure they ate all of their lunch. It was tons of fun, although not particularly challenging.
The other was more aligned with my interest in education. I worked as an English teacher at a neighboring villages elementary school. It was about a 30 minute walk along a deserted dirt road, but I wasn't complaining. It is through beautiful country side and I would often see troops of howler monkeys swinging through trees. It was hot, but as often as not a Tico would offer me a ride in a car, back of a truck, or once over the rear wheel of an ATV that already had four other people on it. I really enjoyed teaching the 4th 5th and 6th graders English. They were keen students and did well even though they were starting from zero. I also raised funds to add an English section to the library. My experience there was very rewarding. As an added bonus of living with no English speakers for miles, my Spanish level quadrupled.
ICADS is an amazing program that I would recomend highly. Great for internships in so many areas.