I have done some cycling in that area. We went from Freiburg i. Br. down to the Rhine. On the way back, we were south of Kaiserstuhl, but went over Tuniberg. That was a challenge, but doable. Ths ride occured in September, when they have the Neuwein and Weinstuebe. Except for the occasional mountains, as the above mentioned, the Rhein valley is relatively flat.