We have done breakfast w/ Minnie and Friends at the Plaza Inn in the past on each of our trips. We usually schedule for first in the morning. I am not sure if it is still holds true as it has been a few years since we've been, but in the past since we had reservations for first thing in the morning, a CM would meet us at the gates at the side entrance to the main entry gates (events/special.. I forget exactly what), and then they escort us to the Plaza Inn before the gates had opened. This was really nice because you could walk down Main Street with hardly anyone there except a couple other CMs and a few other people also heading for breakfast.
Another time it was before rope drop, but the gates were opened to let people in to Main Street. The CM still meet us at the gate, but since Main Street was packed, she lead us through through stores and what not to get around the crowds and the rope drop.
We are planning to do the same on our upcoming trip this October (reservation made!)