And another tip - MM doesn't always use the terminology you may be used to. So instead of File/Open its Overlay/Import. You then get the standard file opening box, and you can browse for any type of file anywhere on your PC/network just as you would with Word or Excel. As FF says, MM defaults to file type .mmo, but that's easily changed (but not permanently, I think).
I just clicked on the link you gave, which opened the file in a page. I then just "save page as..", specify a directory when prompted, and it saved it as a .gpx file. Importing that into MM gave be a route with (IIRC) 106 waypoints on it. Quick and easy. No need for GPSBabel etc. And from MM you can dump it straight into your Garmin.
I'm using MM2004 - later versions may differ.