We had an early ADR for Crystal Palace back in February and made sure we got there early since I knew they would let us in before the general public. It was a piece of cake, as soon as you get off the monorail, boat or bus you will see a CM with a big sign and informing people about the separate line for those with ADRs. The time we went the line was all the way to the left, the side closest to the monorail station. It was nice walking into an empty MK and the perfect time to get some photos with no crowds around.