The first thing I have to say is that the staff at iNMSOL is some of the friendliest people I have ever met. They will help you with whatever difficulties or problems you may have. Moreover, if you choose to join some of the trips they arrange, they have knowledge of mostly whatever you need to know. When it comes to Granada for example, they have knowledge both on subjects which tourists need to know, like the history of Alhambra or Garcia Lorca, but also on the funfacts, like who is the creator of the many awesome graphities in the city, where to go for the best tapas, the best flamenco-shows and much more. The staff have been wonderful in giving tips for how to enjoy this fantastic city even more.
When it comes to the learning I don't have much to say other than I can assure you that you will learn spanish. The more important thing is what you get for 'free'. You get to know other people from all around the world, you get some free lectures about where the cheapest beer is sold, what cities to visit, and in general tips that make your life a whole lot easier.
If you choose to live with a family during the stay(which I think is a great opportunity) you get to see (and experience) how the locals does it.
Spanish food, every day? Yes please. Also, if you are staying here for a long time, it is nice to have an acommodation while searching for your own place to stay.
If you want much value for your money and have a really nice time, I think iNMSOL is a really good alternative, and I don't think you'll regret it if you choose to go there.