Well, the rope is placed at the end of Main Street, right before you can really start going different ways. For the Magic Mornings, the rope is not there. There is a different gate area to go to that allows you to get into the park. I have no idea if they move it around, but just look for the signs above the gates...one section will say Magic Mornings.
When they open the main gates for everybody (I think about 10-15 minutes before the offical park opening), the rope goes up and no matter if your MM or not, you will be stopped at the rope (at least that is the way it seemed). Then, once the park offically opens and they do their opening "show", they take down the rope and you can "walk" around the park. Normally people speed walk, because they have CM everywhere telling you to WALK and not run. It is a really fun moment though
As far as DCA, you are really able to get far into the park currently. Once BVS opens, things might change. For now, when you enter the park you go through the long walkway behind Soarin, then you head in front of River Run (and can grab a FP for World of Color). You will get stops before the bridge heading over to the pier right around Little Mermaid. I am not sure if you can go the other way in front of Soarin to start heading over to Tower of Terror or not because my main focus is always grabbing World of Color tickets and then preparing to "walk" over the bridge to get in line for Toy Story.