Meet at Columbus Square or Washington Square. If you wanted to take the A to Port Authority, you could easily walk to Times Square along 42nd. Walk to Bryant Park (another worthwhile destination) to catch the D.

You can get transit directions on Google Map. I've always had really good luck.

I also have an iPhone app called Emark NYC Subway that is really handy.

I don't know if they still have a day pass, but you can do an do an EZ Pay Xpress Pass.