Yeah, the AP is pretty far from the DT. You can't get to Downtown from the airport by train, though.
If you want to stick to the train as your mode of transport, you'll be pretty limited in terms of what hotels you can stay at.
I'd imagine that a room downtown will be impossible to find at a decent rate by now.
Your best bet might be what's known as the Motel Village that is up by the University.
http://www.google.ca/maps?hl=en&lr=&...local&ct=title
It is right by Banff trail station and has a little pack of 4 or 5 motels in it.
Then again, if you want to be close to the action, you might want to check out The Carriage House Inn on McLeod which is very close to Ranchmans, and isn't a bad cab ride, bus or walk from with Heritage or Southland Train Stations...