In September 2012 I signed up for 4 weeks of Spanish classes at Intercultura, first 2 weeks in Heredia and then 2 weeks in Samara. I had a great time, both in the classes and living with the homestay families. I think the 2 campuses are relatively similar, both with skilled teachers and attentive staff, but the surroundings are quite different (urban vs. the beach). For that reason I'm happy I chose to experience both of these places. As for the language course itself, even though interesting and fun, I wouldn't exactly call it laid-back.
There are 4 hours of classes each day, but you also need to practice a little bit on your own and there's usually some homework too. Thanks to this relatively quick pace you can feel the difference and see your progress each week. I had no Spanish before, but after these 4 weeks I'm able to understand a whole lot and I can express myself to a degree. Obviously you can't become fluent in a new language in a month, but you'd be surprised how much one can advance in only a few short weeks.
Staying with a homestay family is also a great way to be more exposed to the local culture.
The families in Heredia and Samara are different, and the living environment in the latter is often basic, so you need to be a little open-minded and not expect 5 star hotel amenities. With that said I can report that I've enjoyed my time with both of my tico families, learning about their lives and especially eating all their delicious food (though truth to be told there's a lot of rice and beans involved). All in all, I can recommend Intercultura without hesitation to anyone wanting to up their Spanish skills and being immersed in the Costa Rican way of life at the same time!