How much Spanish will I be able to learn through a month-long immersion program?

I think that aside from what you've already done, that this is the best thing that you can do to try to improve upon what you've already learned. Without actually seeing how you speak/understand it's hard for me to say how much you'll improve, but I would think it would help a lot since the best teacher is always experience, and that's what you'll get by being surrounded by Spanish all the time. Plus Honduras is a beautiful place. :)