Yes, that's exactly how it worked for me. And very well, too.

As I wrote in my other post, it works until someone inadvertently reverts to Swiss German, and then the others, completely naturally, follow suit, (without even realising it) back to their mother-tongue. Then I'd have to ask again. That's why I wrote: "Repeat".

It was my experience, when I still needed mother-tongue Swiss German speakers to make that special effort for me, that they were mostly very accommodating as long as I asked them politely, yet then only for as long as they remembered and were not triggered to revert to what is, after all, natural for them. Then, when I reminded them, they said: "Oh, sorry!" and switched back to Hoch/Schriftdeutsch. Repeat.

As I see it, one of the key things that help, when integrating into a country or language zone, is to accept that the locals are going to, and will, and are free to, and have every right to, speak their own language the way they speak it in their own area. That's just nature. The local language is part of the basic cultural fabric of any place. It is neither better nor worse not bluer nor greener than any other language anywhere else. It is what it is, and that's the fact of the matter. The sooner one develops ways to deal with that, amicably, the easier life gets.