I assume by CR you mean Contemporary. Without a car, fastest way is to take a cab (readily available at valet service at the hotel and trip time 10 minutes or less). Disney way:
1. As long as MK is still open, walk over or take monorail to MK and catch bus at depot there to Beach Club. Return same way if MK is still open. One way trip time 30 minutes. Note if this route is not available either way, then you should give serious consideration to that cab, as other ways will take longer.
2. If above route not available because MK is closed, then check to see if MGM is still open for time of going and return. If so, take bus from Cont to MGM, then take boat from there or walk over to BC. Return to MGM and take bus to get back. Trip to MGM is about 20 to 25 minutes and trip by boat or walk from MGM to BC is about 15 to 20 minutes.
3. If both MK and MGM are closed for either leg, then you still have two options: a) the dreaded trip by bus to Downtown Disney from your rersort and then catch a bus from there to BC and reverse going back (dreaded because it can often take an hour or more); b) if Epcot is still open, you can take monorail to TTC and then one to Epcot and walk through Epcot to International Gateway entrance near United Kingdom and walk to BC from there or take boat -- that trip can also take more than an hour as you have to walk through Epcot; moreover you would need to use a park pass to enter Epcot.
