Austria-Germany cycling guides
I showed my honey, who is German-Canadian and can read /write basic German.
He has cycled on several different trips in Germany and just returned from Europe this spring.
He recommends if you possibly can to get these guides: http://www.esterbauer.com/ I got this website off the back of a real book guide in series for the Rhine Valley area where he did go riding.
He knows someone who cycled by herself from Germany to Denmark, using one of these guides. A great help since she could not read German signs nor spoke the language, etc.
I'm sure our good TE European members will respond here. But most likely you WILL encounter some people who can speak some English. In fact, probably maybe even many touring cyclists on the path at this time of year.
Tell us about your journey soon!
Österreichischer Camping Club
Hi! When I was in Vienna two years ago I thought about doing the route and visited the Österreichischer Camping Club shop. It's just outside the inner city, off the Schubertring (http://maps.google.com/maps?f=q&hl=e...,0.012231&z=16). They had a guide book in English for the Danube route. Could be the same one you have, but it might be worth a look if you have the time to check it out. They might have some other resources as well.
Have fun! It's a beautiful area.