I went to Spain and spent 3 months in both Madrid (2 weeks) and Algeciras (2 months). I definitely recommend traveling abroad to anyone and everyone with the opportunity to do so. It is a unique experience that gives you a valuable perspective on your current life, no matter where you go.
With this program, you are teaching English to the children of the host families. I would almost always speak English to the kids and spanish to the parents. For me, the teaching was mostly conversational and I really liked that about it -- it's a breath of fresh air to get away from the books for a few months. There is a lot of time to hang out and do fun things while technically "working". For example, we went to the grocery store to learn names of fruits and vegetables, we learned conversational vocal while watching Harry Potter, and we practiced our grammar while writing letters to each other. The program is very open to your own interpretation of how you want to teach. That's the best part about it.