Italians : outright joy combined with the immediate switch of language. If from the same region, some family link will be eventually uncovered.
Germans: Slight annoyance. Yet another German; there are so many in every freaking corner of this planet. Maybe a switch to German if nobody else is around and some friendly chatting but not necessarily so.
Belgians – Wallonian and Flemish: Irritation then enjoyable surprise. Speaking English, it is actually possible to communicate with each other and chat about beer, chocolate and the stupidity of Belgian politicians.
La puce, die Welt and everything else 