I realize this thread might be a little old by now considering the decisions are about to come out, but for the sake of future visitors I’m going to add to it.
First, CLS isn’t really geared toward people who don’t already have a vested interest in particular languages. There are complete-beginner classes available in most languages, but generally speaking the program is aimed at students who already have at least some idea why they would want to learn a specific language in an intense setting. It is not for people looking to simply get cultural exposure, nor is it intended for those seeking to take a language for cursory familiarity only to move on to another language the next year. None of the things I just said are worthless and I definitely encourage people to look for cultural exposure programs and opportunities intended to simply broaden one’s perspective- but CLS is not one of those programs.
Second, CLS is really intended for those planning to use the language they study in their career field. You should be able to articulate a specific reason for becoming proficient in your chosen language- CLS is very serious when it asks applicants how they plan to pursue proficiency or fluency after the summer has ended. That doesn’t mean you necessarily have to want to get a PhD in Chinese Literature to take Mandarin through CLS, but you should think long and hard about WHY, professionally and academically speaking, you want to pursue a specific language- not just take it for a summer because you think it would be fun. CLS is certainly fun, according to my friends who have done it years prior, but it is also extremely intense, especially in languages like Persian and Arabic where you study not only the literary/standard language but also regional dialects that can differ quite greatly (Persian is taught in Tajikistan, where the language is written in Cyrillic instead of Arabic script used in standard Persian, and Tajik is almost unintelligible to most Farsi speakers).
CLS is highly competitive, regularly admitting massive numbers of top language students from top schools, along with many talented students from a large number of other colleges- with an average acceptance rate hovering around 10%, making it more selective than some Ivy League universities. The application process alone is stressful enough, but the program itself is for students who are very, very serious about their language studies- keep that in mind when considering whether to apply.