As always, I agree with
LizzyM above. Definitely stay with students if possible. Not only will you save money , but it's a great way to get good information about the school. However, if that option is not available, I would stay in a hotel. I would not go with AirBnB. Again, I would try to eliminate random problems as much as possible. Go with a known quantity for a bit more money. Don't be penny wise and pound foolish.
Taking the bus is a great suggestion, but for trips of a mile or so, if the bus isn't there, walking will often be faster than waiting for the bus, especially if there's traffic.
If you do plan on taking a bus, make sure that the bus you want is listed as stopping at the bus stop you're waiting at, and be sure to get on the right bus. Even the buses can be complicated.
If you do walk, make sure you are wearing comfortable shoes, or else wear running shoes and bring your nice shoes in a leather portfolio/purse. That's what many women do in Manhattan.
Taking the subway might take you out of your way, and you might end up walking more just getting to and from the subway stations. You definitely don't want to try to learn how to use the subway system while trying to get to an interviews.
Once you know when you will be there, and get a hotel ( ask me, Gonnif, or LizzyM to help you select one ) we will be able to tell you how to get around. But if you stay in any of the locations that they already suggested, walking, the bus, or a taxi will be the best way to get to your interviews.
Needless to say, you absolutely shouldn't consider renting a car. That's a terrible suggestion. Don't even think about trying to drive in Manhattan!