I think HE is talking about the one for undergrads.
Yes it is very competitive, as I applied for it and the IRTA (the one year program) one after school but did not get in. I don't remember if I applied in March or February. But as most of the PIs who I personally contacted told me, it is very competitive and although I was a good enough candidate, they were full for the moment. I think your best bet is applying early, and if you are applying for this summer, I think you are almost late.

But I'm not so sure.
I think they give you a housing discount in one dorm of a school that is close to them. I think American University.
Again all this information is on their website. Your best bet would be checking it out yourself.
I know you need about 2 or 3 letters of recommendation etc etc. Goodluck