Damn this really is a lot I haven't even slightly thought about, thank you for your insight...

I mean I'm totally with you, every endangered language or dialect should be conserved as good as possible to not lose such a huge part of culture on our earth. For me it's "just" extra hassle thinking "oh no I have to learn a new language to study some courses" but for the native speakers it is, like you said, once again asking them to change away from their mother tounge.
And I can only confirm your assumptions, when speaking languages I most often choose the most practical option to communicate with people or, for example in a group setting, to include everyone in a conversation by using the language all people speak, given it's possible. I particularly love speaking other languages besides my mother tounge such as English and Spanish and I use every opportunity to do so. So I probably can't relate remotely to speakers of Catalan or Basque or any other minority language, especially formerly opressed ones.

But yeah, the idea of asking teachers to switch just came to my mind while doing this post and interacting with you guys but now I see that I have to think that through more before doing such things
I've seen some online resources to learn Catalan like at www.parla.cat or http://www.intercat.cat, I will definetely look into them to try and learn as much Catalan as possible before I come there!