Earlier quoted context omitted.
Like not speaking the local language of any country : won't work in the long term.
I disagree. Not every country is the same. I was in Berlin, and I was never spoken to in German (since I don't really look German), and I would ask the person if they spoke English just to be polite before I started speaking to them, and they would almost get offended. Actually, I hardly heard any German being spoken. On the contrary, in Warsaw I had problems getting basic directions in English even if I asked young…
I can tell you that not speaking german was really a burden (again in the long term).
Everyone below 40 speaks english, but as soon as you have to deal with the administration, or just even the doctor, it really was a PITA.
Also, Even the tech support (e.g. for Internet) wasn't allowed to speaks English on phone.
I'm pretty sure the same "issues" apply to any country.