Quite true. I remember a very confusing exchange when asking for directions in Albania (which has a similar tradition). The man who I was asking was clearly aware of the cultural difference, so began to compensate for the benefit of this hapless tourist. And so did I. It got to the point where neither of us was quite sure whether the other was saying yes or no. I ended up with a spaghetti bolognese and a beer, rather than the directions I wanted

For Bulgaria, my top tip would be to learn the Cyrillic alphabet before you go. It won't take long, as many of the letters are easily identifiable - but the ability to read signposts is underrated until you lose it. And your map, with road names in Latin script, will be useless if you can't read the road signs.