That's where I'll be in a week. I'd suggest looking into hotel prices well in advance. Turns out, the Wednesday night that I'll be there is just about the most expensive night of the week! Most mid-range rooms are going for $300-$400/night - at least around Central Park on the South/West? side. Next trip, I'm hitting up a Groupon/LivingSocial deal and will either stay on Long Island or get a place in Manhattan again, but I sure won't be paying the same.
I've heard the same thing from about everybody, that the subway system can get you pretty much anywhere you want to go.
Hey, next week, I'll be manning one of the HP booths at the Interop show at the Jacob Javits Center -- either booth 119 or conference room MR731.
Not sure if I.T./Networking is your thing, but if it is, stop by, if you get a chance!
Yes, the subway system in NYC will take you *anywhere* on one fare, either directly, or by transferring from one subway train to another. You can even transfer to/from (between) subway and bus on that same single fare.
Here's an online subway map: http://mta.info/maps/submap.html
...or a PDF version if you prefer: http://mta.info/nyct/maps/subwaymap.pdf
Hope this is helpful!
-Sean