Miss Jezebel DuPree2 said: "Bring a no-doze... that play is a snooze-fest...."
The OP didn't ask for your opinion on the play.
Unfortunately, I don't have a first-hand answer for you either, OP, but I do have some experience at this theatre, and with stage-dooring Off-Broadway shows in general. I think the actors come out of a door near the bathrooms in the main lobby - I'm not positive about that so you should ask an employee when you get there. Because of the nature of the show and production, I find it unlikely that they would choose to slip out another exit. There will probably only be a few people waiting. If you just keep your eyes open for them after the show, and approach them, I doubt they would refuse a photo or autograph.
I'm not sure exactly which theater this play is playing in the complex, but when I saw SWEET CHARITY the actors just walked right out of the main theater entrance. Sutton and others were very happy to sign/talk to the small group that had formed right outside the main door.
"Oh look at the time, three more intelligent plays just closed and THE ADDAMS FAMILY made another million dollars" -Jackie Hoffman, Broadway.com Audience Awards
I would just wait in the lobby area upstairs. There's a bar. There's seating. If they're prepared to come out and sign, they'll wait for the audience to leave and it should be pretty relaxed... not like the typical stage door experience lately with the barricades. Not that this means anything, but I saw Zosia coming out a show once (as an audience member) and she wasn't exactly being mobbed so I think you'll be fine.
During my last trip I stayed Yotel and frequented Treehaus next to Signature a lot. (Great little café, with an incredible hot food bar). Zosia was in there a lot. I think it was during rehearsals. She was always nice. I didn't ask for photos or signatures but she was friendly to chat with.
"The sexual energy between the mother and son really concerns me!"-random woman behind me at Next to Normal
"I want to meet him after and bang him!"-random woman who exposed her breasts at Rock of Ages, referring to James Carpinello