Hey MLXX,
I learned German as an adault and can tell you that you can get functional enough VERY QUICKLY if you apply yoursself and work with enough effective approach..
I did 6 months of back to back 6 week condenced University of Maryland semesters (means I did 4 of those)... that got me introduced to the basic structure of the grammar and some vocab... which is enough to carry yourself the rest of the way if you try. This was on a military base night school. You will likely NOT be doing that.
You can take night classess at what is called Volkshochschule (A kind of school for adults covering many kinds of real cool topics (even Italian cooking)... now these are immersion right from the beginning, so you should supplement early to keep even if needed... but I can tell you I see all kind of my foreign friends from there who applied themselves and worked hard... after 6 months, they could function quite well.
My belief about Germans towards foreigners (a type of foreigner) is they hate it when the foreigner demands everything... especially demanding communication be done in English, even though the person has an abiloity to work and learn, but did not (assumed to be because they do not want to)... I think Germans do not resepct that at all and I think i pisses them off. I would agree with that. If you are in another land for a long enough time and want to function there, then you need to do the work and effort. Many will not attempt as they do not want to fail... and you will fail a lot early on, but you fight through it.
I believe German respect those why are trying to work towards learning the language and culture and show true effort... to these kind, I think Germans give extra leeway even if the foreigner is not doing very well early on.
I would advise you make friends BEFORE you get to the area you intend. BEFORE. Make known what you want to do. Ask what night school operates when. Get with whatever club you like and let everyone there know what you are trying to do. I think you will be surprised at the support you will get.
Personally, I think doing this kind of thing is a real blast. People in the world, the average citizen do NOT usually have an opportunity to go to another country and operate there... so if you can go there, learn language/culture and fit in, it is very enjoyable in many ways.
You asked for real Germans to reply, and you should hear what they say as they are there and they are the real Germans. I provided my input as I did what you are trying to do in a different way way back in the day.