Anytime between now and about two months before the wedding. The closer to the date, the more expensive things will be and Thun is a popular destination in the Summer so hotels start getting booked out by February!
The train is our usual go to, but there are a lot cheap flights between European countries. For example: EasyJet, RyanAir, EuroWings etc. For the train, look into a Eurail pass. Even if you are just travelling around Switzerland, look into potentially buying a pass from them as tickets can be significantly discounted For example: -If you book directly using the SBB app, a one way ticket for an adult from Zurich to Bern is $68 Swiss Francs (approx. $80 USD & $109 CAD). -If you get a Eurail pass for just Switzerland, it gives you 4 days of unlimited travel in a one month period for $317 USD ($430 CAD). It's worth it if you're planning on doing some bigger day trips. There are also other options but here is the website: https://www.eurail.com/en/?gad_source=1&gclid=Cj0KCQjwi5q3BhCiARIsAJCfuZn9aClIWudk1vziFgFoEVsLQaSYdafsupLfoajdqs5OeHJ8Hxb_k8EaAm4YEALw_wcB&gclsrc=aw.ds
The four national languages of Switzerland are: Swiss German, French, Italian, and Romansh! No need to worry though, most Swiss people speak english and are very accommodating!
Yes! Most cell phone providers have daily international plans but often cost at least $10/day which can get pricy. When you arrive in Switzerland you can go to Swisscom or Salt to get a tourist sim card. They have kiosks at the airports or at major train stations (Bahnhof) -Swisscom has a sim card that has unlimited data, and unlimited calls and SMS within Switzerland for 20.- ($23 USD, $32 CAD) for seven days.
Yes! Most places will take card now (except amex) but it doesn't hurt to take out some Swiss Francs. You usually get the best exchange rate when using the bank associated with your debit card.
In some cities like Zurich, yes. However, Bern and Thun do not.