The crowds getting to the walk are worse than the ones getting into the park afterwards, which are pretty terrible. First, you have to walk from M&F, there are no shuttles running. I didn't try to enter from the Harbor side, that may be possible, but this is how it was from DtD. When we got to the security lines, they stretched to about the door of La Brea Bakery. There were large groups, like 30-60 people trying to meet up in the area, mostly near the fountain. It was almost impossible to tell which was a group getting together to pass out wristbands, or who was in the security line. Fortunately we picked up our wristbands earlier in the week, so we didn't have to meet up out there in all the chaos, but we still had to get through security, and aside from all the groups meeting in the area, there were also groups trying to go through security together, which led to so. much. line. cutting. We actually missed meeting up with our group. Then when we got in the park, there were even more groups trying to meet up, we couldn't get through the tunnels on the side of Main St because so many people were gathering their giant groups right in the walkway and we couldn't get around them. Eventually we broke through, and just started moving through the crowd until we got stopped near the Main St Cinema. At this point I was with one other person and trying to text some friends who were further up in the crowd. We couldn't hear any of the announcements, but the crowd was slowly inching forward, and then suddenly as we passed Market House we heard the starting fireworks and realized we were walking! The crowd stayed shoulder to shoulder around the hub, but we stopped for a pic with characters at the castle, (lots more line cutting there) and it did thing out a little. We never did meet up with our friends in front, but we did end up stopping for a second photo op for some friends who arrived and started later. They eventually decided to skip the first part of the course and meet us where it doubled back. By the time we met up with them it was pretty uncrowded, except for the water bottle station and mush easier to move around.
Basically, this isn't like a 5k running race. There were strollers, kids being pulled in wagons, people walking 3-4 across holding banners and even heard there was a team tossing beach balls back and forth. But the thing is, you're not required to start the walk at the exact start time and you're not racing everyone else, so with that in mind, try not to stress out about the crowds and everything that comes with them.