When I first moved to Germany, it was really nice that so many people could speak English. If I was lost or got a broken leg, usually someone could help me out in a sensical way pretty quick. Now that my language skills are apt, however, it really bugs me when people insist on practicing their English on me. I came to a foreign country to learn the friggin' language and not as a walking English instructor. I find it so ostentatious when someone insists on speaking English and another insists on speaking French or German or whatever language suiting to the location. It's not fitting to any social situation.
For those of you who have no experience in the matter, it's difficult to clarify precisely how the feeling is. Perhaps it would be like having a very thick accent, a Grundy County accent, for instance, but having the ability to tone it down a little bit so that if you're speaking to some unknowing Yank, you two could better understand each other. The example doesn't really work, though, because the Yank would never want to practice his/her Grundy County oral comprehension skills.
Being the polite young lady that I am, I usually, loathingly, in fact, break down and speak English with the person. How do you politely inform them that it's only just that they speak in their native tongue? Honestly the whole matter is about as awkward as a tit popping out of a topless shirt; not like that's ever happened to me or anything.