I agree with Sinfonian, you never know. If a performer threw up right after the curtain call, she/he probably will not stop to sign. Sometimes they are just tired and will not sign, and some are very nice and are open to signing, photos, and short convos. He is also right about WICKED. I saw it on a Saturday evening, and stage dorred afterwards. There were maybe 10-15 people tops. But BOM is hugely popular right now, and the stage door likeley will be extremely crowded. Especially on a Friday. And it doesn't help that you are in LA.
Theatre is my life. No one can take that away from me.