Since there are no buses running resort to resort - in this case, POP to BW - you cannot guarantee you will be there on time.
The buses start running to the parks from the resorts at 6:30 am, but the buses running back to the resorts may be sporadic. For instance, you could go to MK and then wait for the bus to go to the BW, however, it makes multiple stops - it will stop at YC and BC before it stops at BW. Then since it stops at the front of the resort, you have to walk all the way through the resort, onto the BW and then over to Kouzzina...... best to take a taxi.
You can request one at the baggage services desk at the curb; they will call one for you.
When you are done with breakfast, the regular bus service will be running at regular service closer to park opening, and you can take a bus back directly to one of the parks. Remember, after it picks up at BW, it will then go to Swan/Dolphin - the last of the two spots - before you go to the park.
Or you can take the boat over to Epcot or HS, which is right on the Boardwalk; also a wonderful ride. It takes the same loop as the buses, so it will go to Swan/Dolphin, BC, and over to one of the parks. You will not go to YC, because it is the stop before BW.
Enjoy!