CapCon, first of all, while your Deutsch will come in handy ordering the beer after your flight, you don't need it for ATC - they are excellent and speak English. The only places you might need it are really, really small airfields, but even there pretty much everybody does speak English.
You will most likely be assigned a discreet squawk code when crossing into Germany, if not, there is one anomaly: below 5000 ft the VFR code is 0021, above 5000 ft it's 0022 instead of the 7000 you're probably used to.
Can't comment on the airfields around Munich, but most people based there seem to use Augsburg.
The Austrian Alps are a great place to fly, but DO brush up on your mountain flying beforehand !! If you don't have any experience, ask a local to come with you on the first flight into the mountains. The hazards, btw, are not limited to the usual wx-related dangers, but also be very aware of hanggliding and sailplane activity, especially on weekends. As you say you'll be going in June, consider very early starts for your alpine flying, as thermals (and TCs) tend to build up starting late morning. That said, a flight through the Alps on a cool morning is one of the best things you can do in a small a/c
PM me if you need some local contacts in Austria.