Interlaken

So far my overseas touring has been restricted to France, but I'm toying with the idea of going to Switzerland next spring, possibly based on Interlaken.

I'm undecided about whether to travel south through France as far as Geneva, or to go through Germany up the Rhine, or to cross over through the Ardennes. Does anyone have any advice to offer as to the best route to take and also any recommendations for sites to stop at on the way there and back? We'll probably go for at least a month, and the stopovers will probably be for two or three days each.

Another concern I have is about language. My French is not very good but I can just about get by, however I have no German at all. Will that be a problem in Germany or Switzerland?

Any advice or suggestions would be much appreciated, thanks.