They do let you in at 4pm. At 6pm the park will close and it gets a little chaotic. They make everyone who has the MVMCP tickets go to Liberty Square and Frontierland. You can go on all the rides in those two areas, but the rest of the park shuts down until they can clear the people that aren't supposed to be there. Try to make your way over to these areas before 6pm so you don't get caught in those crowds. We were just there last week. We had a great time. Enjoy yourself.