I'm an international math student who applied to five PhD programs in the US. I have been admitted to the University of Michigan and Purdue, but have not heard anything from the other three (Caltech, Brown and Stony Brook).
I'm planning to visit the University of Michigan in nearly two weeks from now for their recruitment weekend. Since I will be in New York first, visiting Stony Brook and Brown will be convenient enough. But that gives me less than two weeks to hear back from them and schedule meetings with the people that interest me. How long should I wait for a response before I contact them? Is it "normal" to visit a university you haven't been admitted to yet?