<p>Just as there in English classes in the US, there is a wide variety of (1) quality of language schools, and (2) diligence with which the students apply themselves to their studies. Obviously the OP should not go to one that does not have a good reputation. She should try to find others who have been if possible (which is exactly what she is doing here), and ask the school for references (and check them). I have friends, who happen to be adults, who went to a language school in Belize for a month. They had a great experience and improved their language skills a lot. You are making a very broad generalization to say that none of them are worth attending.</p>
<p>OP, you might try looking at college websites to see where they are sending their students. Then contact the language school directly. Although if you are in college now, your college would have to approve the credit transfer (and if they offer a similar program, they probably would want you to do theirs because it is more profitable for them…).</p>