Yes, the wind is mainly North-West. This is the reason most people cycle the Elberadweg from Hamburg to Dresden and not the other way around. (Normally you ride along rivers from the spring to the mouth, but not in this case.)
From Berlin I would take the R1 and then the Elberadweg to Dresden. Back to Berlin I would take the Spreeradweg or at least a route that runs similar to it. Note that I haven't cycled this route yet - I only covered the Elberadweg further north. But looking at the maps and from what I've read in preparation of a future tour just like yours this is the most sensible route. Chances are high that you'll have the wind in your back on the Elberadweg and when you cycle back along the Spreeradweg you'll have cover from the trees.
http://www.radeln-in-brandenburg.de/webgis/index.html?TourId=_196http://www.radeln-in-brandenburg.de/webgis/index.html?TourId=_187I strongly suggest you contact katjob, since they (katjob are kat and job, a couple) live in Dresden and can help you better with details