15483 posts
Hi Piper2, welcome to MySwissAlps!
You can find the quickest route in the timetable: http://www.myswissalps.com/ti metable. This can easily be done in one day as it takes about 6 hours, but of course spending some time in Geneva, or Lausanne, could be a nice break:
This page might be useful for you as well: http://www.myswissalps.com/tr aintickets/france.
I would stick to the train, not switch to a bus. That won’t speed up the trip, nor will it be more comfortable.
72625 posts
One day should be fine. Wengen – Geneva is about 4 hours, Geneva – Lyon is around 2 hours trip. You can do it about 5 times per day (the limiting factor being the 2-hourly Genève – Lyon expresses)