Do you have GPS files or way points already, or are you trying to build up the route yourself?

Can you load the GPS files up into something else, like Bikeroutetoaster or MapMyRide, and then load into the Garmin?
The ACA files are cluttered with all kinds of other non-route waypoints, so they are really hard to use.

If you are building it up yourself manually, Bikeroutetoaster is great.

You might get help at the ACA forum as well: http://www.adventurecycling.org/foru....php?board=3.0

And there's someone over there who posted gps files for the route on his site, which was a big public service - thanks tsteven (if you are here too).
http://tsteven4.qwestoffice.net/