General, welcome to NYC! You'll find the Midtown area of Manhattan to be quite safe. Crime in New York is WAY down, in fact at forty year lows. The flip side of that is that you will have to limit your carry knife to under 4" and no auto's allowed. Don't even think about carrying a hand gun or a straight blade in a sheath!
There are hundreds of hotels in the area of the Custom show, but none might reasonably be called "cheap". Housing is always an issue in NYC, even for visitors. I would get on the net and check around. The good news is that transportation is convenient in Midtown, and everything is within walking distance! New Yorkers walk more than anyone you've ever met and most of us are not nearly as obnoxious as you've heard!
Anyway, have fun in the Apple, and I hope to see you at the show!
John.