For an English speaker, what would be the most useful second language while spending time in this area?

It totally depends on what parts of each country you will be in. German is an official language in three of those. Although in Switzerland it's more Swiss German. French is highly spoken in Switzerland as well and obviously France. Alsace has some German fluency. Just learn both!!

English

Try to say some German words if you know them and then tell them you're an American and ask if they speak English. The Germans and Austrians all know it.

Just be cool and they'll have no problem speaking English.

If you get a really old shop attendant, they might struggle with English. All the young people know it.

At least that has been my experience in Southern Germany and Austria.

We just got back a few months ago from a trip to Germany, Austria and France. Just about everyone you're going to deal with speaks English well enough to understand you.

I live in Switzerland and travel extensively throughout Europe and beyond…you don't need to learn French or German. Everyone you run across in a service industry location will speak English. Perhaps it may be a good idea to know what will be said to you for hello, good bye, thank you, your welcome, etc.,…but once they figure out within .02 seconds you don't speak the local language they will speak in English.

With that said, with me living here, yes, I'm a doing ok with the language but it takes time. You're not going to pick it up to be useful in a short time for a vacation…so work on the basic words/phrases and then enjoy your trip.

French is as useful as teats on a bull. Even if you spoke French perfectly they would continue to be obnoxious.This also includes Louisiana. The only exception would be in the Normandy area. English will work out OK for you in the rest of Europe. However always attempt to start a conversation in the language of the country that you are in. 90% of the time they will merge the conversation into English. (France would be the exception)

English, then German

I've had good luck by knowing hello, good day and thank you in as many of the places I fly to as possible. Most speak English well enough to communicate with but they seem to appreciate a few things in theirs.

The more the better, but even a few mannerly phrases help.

I have been to Switzerland, Austria, and Germany several times. In those trips, I have met a total of 2 people that spoke zero English. One had to be 95 and was obviously suffering from dementia (based on her interactions with her daughter-in-law, but that's another story) and the other spoke Spanish, so we were able to get by. I did have trouble with a Swiss border guard who, despite speaking English well, just wanted to be an *******.

You're fine with English but knowing your bonjours and auf weidersens won't hurt.

This all reminded me of the time I was driving from Lithuania to Warsaw in the middle of the night and came to a border crossing where nobody spoke English. They tried Lithuanian, then Polish, then got frustrated, but when I held up my American passport the guy smiled and exclaimed "America, Donald Trump #1!" and let me through.

I just returned from a trip to France, Germany, and Belgium.

I found if I make an effort to say a few things in that country's language, the people were very helpful and most spoke English. Learn hello, thank you, and similar phrases and it goes a long way.

For example, in Paris, I stopped into a small coffee shop/cafe place for breakfast. I asked for orange juice, they looked at me like they had no clue what I was talking about. I tried du jus d'orange, and boom, everything else was in English.

The one time I encountered someone that knew zero English, I was able to use my phone to translate.

I can only speak to Paris, but when we went earlier this year, the majority of people spoke English. The only time we had a language barrier was telling the bums to piss off. A stern hand up motioning them to F-off was sufficient.

I've found that in France observing the social custom of immediately saying "bonjour" or "bonsoir" when entering a shop and the "merci" or "merci, au revoir" when leaving goes a long way. I will echo that everyone speaks English for the most part, and the French outside of Paris are reasonably friendly.