Cd is just the co-efficient. CdA brings area into the equation, and yes, total drag is the thing that matters. "Average" is pretty subjective due to styling differences between bikes. I don't have the science handy to back me up, but I'm pretty sure that my tourer isn't as draggy as a Harley with no windshield or fairing, and I'm pretty damn positive I'm not pushing as much air as a pickup truck.
What matters to me on that vehicle is
smiles-per-gallon.
