We got up early to try and catch the first shuttle (6AM) at the visitor center. We arrived at 6:15 and had missed the first shuttle so we had to wait in line. There were enough people in line that the 2nd shuttle filled up quickly so we caught the 3rd one. I would recommend arriving at the park early as overall there are fewer people in the park and the temperatures are cooler. It was almost 80 even this early in the morning. Highs were expected to be over 100. I would also recommend taking the shuttle to your farthest stop and working your way back towards the front. There were people who got off at the first stop and wanted to get back on the next shuttle but the shuttle was full and no one got off so they would have to wait until a shuttle arrived and some people got off.