Personally, I do try to learn the local lingo (at least basic words and phrases necessary for travel) prior to visiting a foreign country, in part because it makes my life easier but also because I consider it to be somewhat rude not to, but I guess I'm in the minority.
"Reports out of the United Kingdom say many of its citizens believe US policies and culture are making the world a more dangerous place to live. Some Australians think we're dumb, obese and arrogant; they use the phrase, "Oh, that's so American" as a put-down.
Keith Reinhard, a former international marketing executive, says, American travelers are often at fault for such sweeping stereotypes. Too many have scarce knowledge of and little regard for the cultures and norms they encounter. All too often, they talk down to their hosts."
Taking the 'ugly' out of 'American' in eyes of rest of the world