Obviously you have to visit Marcelo. He just had surgery which is a bummer, but he is usually on the mat, doing the whole class with his students - even warm ups. But Paul is an amazing instructor, and Bernardo Faria and many other great competitors are there too.
Renzo's is a must visit as well, but I wouldn't get your hopes up to see Renzo. You might catch John Danaher at his morning class, though.
I know there are other great schools but those are the two you hear about.
Off the mat, it depends on where you are staying and what you are into. 9/11 museum was powerful. Chelsea Market was a lot of fun. Highline was a nice walk but it might be a bit cold for that come November. My most basic tourist advice would be to steer clear of the usual tourist traps (ie Times Square) or at least wander a ways from them, talk to locals, and make your own discoveries.