The train is a better idea than Greyhound. Bikes sent on Greyhound usually go separately, by truck. The train is also more civilized.
If you are flying into Vancouver with your bike already boxed you can get on a connecting flight to Kelowna, Kamloops or Calgary and start your trip from one of those cities and ride back to Vancouver without having to use the train or bus.
Jasper to Vancouver can be cycled in 5-6 days.
http://www.crazyguyonabike.com/doc/3036