How about the Hirschfeld? Since Saigon is probably going into the Broadway (where else?), I think that the Hirschfeld would be a good fit. Plus, I could see Kinky Boots closing.
The stage door is on Church Street on the side of the building, just down the street from the main entrance. A loading dock and stairs are there, and it is very easy to find. Last Friday, basically the entire cast came out and signed. Every one of the leads, and especially Christy Altomare, was so gracious and lovely and excited to talk with us. It was the most friendly and welcoming stage door experience I've had. The show is absolutely stunning, by the way. One of the best shows I've ever seen (and I've seen a lot). Have a wonderful time!