If you don't have a car then I would suggest getting a taxi from your hotel there. Do that one way. Then after breakfast the Disney buses will be in full swing. For example plan that day on going to HS or Epcot for the day or take the boat ride to HS to catch buses there to take you back to hotel. Or catch the bus at Beach club if going to other parks including water parks or even DTD.
Catch bus at your resort to any park but Epcot(no bus to beach club from Epcot) or DTD then catch the bus to Beach Club resort. After you're done if not going to Epcot or HS(there is a boatride or if going to Epcot there is a 5 minute walk to World Showcase side) you will catch a bus back to DTD(where you can take boat to POFQ) or bus or you can take bus to any park and then catch a bus to your resort.
All resorts provide buses for Resort breakfast reservations that begin running at 6:45 AM. Check with your Concierge and see whether an Epcot or HS bus will take you to BC. We traveled from AKV in May and a HS bus took us directly to BC for CMC.
If you don't want to spring for a taxi, the quickest way is to take the bus to DHS and then either walk (figure 20 minutes) or take the boat from DHS that will drop you off at the YC dock.
We stay at BC a lot and we really enjoy the walk between DHS and BC. And unless the boat is at the dock waiting for you, it's quicker.