Thanks @wildchartermage and @sat0ri ! I'm pretty sure it's allowed – we did discuss it briefly/ casually as a hypothetical possibility, and the response form has a defer option. I'm just more generally curious about the pros and cons of deferring or not. Of course, I don't know if I'll even get the Fulbright and don't want to overthink it beforehand, but at the same time I feel I'll need to make a decision fairly quickly because of deadlines.
I think my (small-ish) reluctance is, that I'm very excited to be a part of a community of scholars in my field, whereas the Fulbright research path has the potential of being a bit lonely. But I still know that having nine months to focus on research is a huge privilege and one I'll surely miss once school starts. Really when I think about it, deferring makes perfect, logical sense, but I'm just so excited about MIT and don't want to wait!
@Satori Yes, thanks, I'm very excited about MIT – it feels like the perfect "fit." I applied to Croatia (so next to Italy!).