As far as the language issues are concerned, I would recommend the French speaking part of Switzerland... I speak just a little French, but I have heard that the Swiss French and the French French are not so much different (the same applies to Swiss Italian and Italian Italian).
As regards so called "High German" and Swiss German - the Swiss consider them two different languages. I have been living in Switzerland for more than 10 years now - and I am still not being able to speak any of the Swiss German dialects fluently (although I understand almost all of them - some of them are easier than others).
Another thing is that many Swiss people prefer to speak English rather "High German", especially if they notice that you are a native English speaker...
If you decide to go for the German speaking part of Switzerland, I would recommend to learn "High German" first - and a few phrases in Swiss German, like Grüezi mitenand