If you can be at EPCOT during EMH evening hours, that is a great time. We did that last week and our wait was only about 10 or 15 minutes. We waited until EMH had been going over half an hour to let the regular park hours line clear out. We had stopped by in the morning on a non EMH day probably 20 to 25 minutes after the park opened and their line was already over an hour-- we went to see Baymax instead and only waited about 10 minutes for him. I would say if you want to do it early or other than at evening EMH, then go there directly at rope drop.