Wisedrum, I made a journey by rental bike from Bernhausen, Baden-Württemberg to Arnoldstein, Austria (not a beautiful town but a good jumping-off place to western Slovenia).
I can absolutely recommend [url=http://goo.gl/maps/iia1H]western Slovenia; the Julian Alps are so beautiful and you will not be disappointed by the Soča River. Hard to believe there was so much history of warfare in that perfect place.
We made it to lunch in Opatja, Croatia on the Adriatic Sea - it has the atmosphere of seaside luxury but the prices are not too high.
Due to time constraints we turned back north for our overnight at a wonderful [url=https://goo.gl/maps/t765Q6zkJMy]family guest house / hotel in Prestranek, Slovenia. They thought I was a German guy and spoke to me auf Deutsch. They were surprised when I spoke English and they could not understand me. So I used my limited German language abilities to establish some basic communication and then everything was OK.
The next day we went to Lake Bled but there were a lot of traffic and tourists. In spite of that, the lake is worth seeing...and hearing. I made this short video and I never tire of it.
We had originally planned to ride as far as [url=https://goo.gl/maps/xevrnWrfZ522]Český Krumlov but due to lack of time it wasn't possible. I still want to see it someday.