I haven't cycled in Germany yet but my partner has done some routes several times...he has relatives who live in various parts of southern Germany. He cycled primarily in the Black Forest/Rhine River region.
This site has some good maps of bike routes.
http://www.eurovelo6.org/the-stages/...folder_listing
If you are near Stuttgart visit The Rose, which is a huge 3 level department store devoted to cycling stuff. My partner was flabbergasted. His cousin took him there. http://www.roseversand.de/output/con...r.aspx?cid=277 You might want to do this stop near end of trip.
If you go bike touring, some of the CHILDREN would put North Americans to shame, last spring, he saw children (10-13 yrs. old) cycling with their fully loaded bike panniers on trip touring with their parents on a bike route by the Rhine.