Our plans always assume that you are starting at the main gate to a park. Since the parks generally let folks past the entrance and into parts of the park before the official opening time, we hope our customers have arrived early enough to be well past the main entrance. In most cases you are not actually allowed on the rides until the official park opening, but you'll have a shorter walk to your first ride than if you were at the entrance. One early morning oddity is Flight of Passage at Animal Kingdom, which regularly begins running 15-30 minutes before the park opens. Toy Story Land had been opening early, but that has not been as regular lately.
We are looking into better solutions for people that will be at the park 30-60 minutes early, but in the meantime, if you are totally sure that you will be at the park early and toward the front of the initial crowd you can remove your first ride from the plans. That way you can ride exactly at park opening -- or before if it's Flight of Passage -- and continue on with your plan afterwards.