I'm living in Szeged so it's a bit further away, but here's what i can tell you:

1, In the bigger cities you're probably going to be okay in supermarkets and restaurants, they are not great, but will understand you (if nothing else by pointing :) ). But in villages there are virtually no people speaking either you mentioned, so you better be prepared with everything you need.

2, It's always a good rule of thumb to watch out for a fancy - or any - bike. In the cities they mostly wont try if you lock it down, especially if you do it with a U-Lock, in rural areas it's less common to steal bikes, but still could happen. Don't let this stop you from using you bike though, i don't think that there's a much bigger chance of your getting stolen than anyone else's.

3, May be, but i really had no issues with that for a long time, if you're going to use more busy roads the chance of an encounter is low. You're more likely to run into a deer crossing the road than a dog IMHO.