Hi. Let me add my two cents to the discussion. I am also interested in strings, so, I hope what I say will be helpful. In my opinion, the top three schools for string theory right now are Princeton, Harvard and UCSB. Perhaps UCSB could be replaced by Berkeley or Stanford in that list, but I personally prefer Santa Barbara (maybe due to its location
). Each of the schools I mentioned pretty much covers the whole spectrum of research in string theory, including attempts of using string theory to (hopefully) describe real-world phenomena. Even Vafa has been doing phenomenological stuff!
Oh, and since you asked about Chicago, yes, it also has a very strong stringy group. Cornell and Columbia are more oriented towards string cosmology.
And about Perimeter, check out my new post