I think that it is only polite to ask whether they speak Japanese or not. Normally if I am meeting a person who doesn't speak English that I don't know, whether they do or not. I think it comes down to good manners. Japan being a polite society would naturally assume that any gaijin would not speak japanese because they don't look japanese. To be polite they would make the effort to address them in English. The same does happen to me when I am out delivering around Leicester and Birmingham. There are many companies that employ Indians that do not speak English very well. I feel it is polite to ask whether they do speak English if they have had a problem understanding you. I never had any problems and have always left on good terms, even if we do not share a common language. Good manners maketh the man. Bad manners make you a ****