Traveling to New York

I will be travelling to New York for 4 days this march with my unlocked iPhone 4s, and I was wondering if anyone had a suggestion for the best way to get basic calling, texting, data for as little as possible.

My initial thought was to simply purchase a pay as you go at+t card but the cheapest rate is $2 a day plus data, which isn't awful, but I have heard at+t's coverage is less then ideal

are there other carriers that you can recommend?

also where is the easiest place to pick up a sim?

thanks for your help!