Buses start running at 6:30am so yes. I got lucky a couple of years ago when going to my 7:30am Kona ADR.. I got to the bus stop at my resort at 6:40am and a MK bus was there waiting and I was the only one on. The bus driver asked where I was going and told her the Poly and she took me straight there since I was the only one on the bus. I thought that was so nice!
Now for my upcoming trip in November, I have 2 adrs for Grand Floridian Cafe at 7:15am and I am not sure I will make it on time even taking a bus at 6:30am.. Do the resort monorails run that early? I'm so confused anymore with the monorail morning start times. I might be taking a cab to GF. I also have a 7:30am adr for Kona during my trip.