No, bus travel from resort to resort is not convenient at all.
During park hours its not too difficult....go to any major park and you can hop on a bus to any resort....but after park hours you'll need to use the Downtown Disney busses to get from resort to resort...and honestly, they're horrible even to get to DTD and back!
I think your BW plan will work to a degree....getting there is quite easy. But you'll probably want to call a cab to get back to CBR. It really shouldn't cost you much since they're not that far apart. You can't get a bus from the International Gateway entrance of Epcot, and you can't get a bus to any other resort from BW. If you're not out late you could either get a bus back from MGM or walk through Epcot to the front entrance....but neither will work after about 9pm.
I'm really not sure about the AK Rainforest Cafe....do they even stay open that long after the park closes? Generally I think the busses only run an hour or two after the park closes...and I think they are only taking folks away from the park, not to the park. Same thing in the morning....the busses only drop off at the parks, they don't pick up (though we flagged down a bus and got a ride when we needed one).
I say just take the busses and Disney transportation where it will work all right, and plan on calling a taxi when it won't....mainly when you're out late. And if you're taking the DTD busses...plan on at least an hour if not more...waits for these busses are long and the busses are often full.