We stayed at POR last week and took the park bus to DHS on two separate days. The bus time showed up in the
MDE app so we were able to plan when to leave the room. We took the bus that came at 5:54 one day and saw an arrival time of approx 5:40 am another day. I watched the app for other bus times and saw that a bus for DHS came approximately every 15 minutes in the early morning.
You might want to give yourselves at least an hour and fifteen minutes to get to the park via the buses.