Having been with my parents and by myself, my experience with just about anywhere I've been is simple.
In the US, if someone walks up to you and starts speaking a foreign language, the average American would be somewhat off-put. If they say in mostly-understandable English, "I'm sorry, my English isn't very good. Do you speak ______?" most people will do their best to accomodate, whether or not they speak the language in question.
I've made sure, when going to a foreign country, that I know how to say some form of "Excuse me, I don't speak ______ -- do you speak French or English?" in the local tongue. I've also found that by putting French first, I less often get the "stupid American" treatment.
Come to think of it, I'll be in Barcelona this time next week.
Anyone care to teach me that sentence in Spanish?