We had a great trip to the Warmnia area of Mazury Lakes, in Poland recently. Here is a link to the photos if you'd like to see what tht region looks like. The left side of this web page has scrollable thumbnails:
http://www.hendricksons.info/mazury/index.htm
It was definitly eary season but we did find some unique places to stay as we went along at great prices.
Another helpful biking link is this one for the Polish train network, in English:
http://rozklad.pkpik.pl/bin/query.exe/en?
Type in your start and destination points to find all the trains traveling between those places. If you check the box for bicycles, it will give you the trains where bikes are allowed. The slow trains are local trains that stop a lot but have cars for bikes and cheap travel prices