When we were there on Friday, it was about 15-20 minutes in advance of opening that people were milling around there. Not forming a line yet per se but it was pretty clear what they were waiting for.
Also of note, though, that FPs were still available into late afternoon (on a MM day). We checked at 2pm-ish and again at 3:45pm-ish. At 3:45 it was into the late night time slots but they were still available. On the Sunday (also a MM day, but we weren't there during MM), they were gone by the time we got to the parks around 11:30-noon. We also noted the lines were longer on Sunday (never saw it under 60 Minutes) than Friday (45-60, but never saw it longer).