We walked the Geneva to LePuy route--did it in two stages (2012 & 2013) because we had to leave the trail midway because of a leg problem I developed.
Our French is poor (our German non-existent), but we had no real problems. Usually, but not always, stayed with hosts who spoke a bit of English. Our hikes were in the spring (mid-May into June). Plenty of rain, but as we have suitable gear, not a problem. I prefer spring because everything is beautifully green with lots of wildflowers. In the Fall, days are getting shorter and probably would be much hotter depending on when. Trail is very well marked. Accommodations are abundant enough--we usually did about 12-mile stages. Often no other pilgrims on the trail. It is more difficult hiking than the Frances, but most other trails are (except Portugal) in my opinion. I loved this Camino--people and hosts very friendly!
If you write me off list with questions, I will try to help. I'm also beginning to write about it on my various blogs. backpack45 "at sign" yahoo.com