English is language of the business world if you exclusively do business in the United States. Even then not really. If you want to target your entire market, you should consider the portion that does not speak English.
I have to disagree with you on those who speak another language and learn English have a greater advantage than the other way around.
Look at most of the classifieds in major metropolitan areas. You see statements as "bilingual (English/Spanish required) Portuguese a plus."
Good points...try practicing law in Miami without a working knowledge of Spanish...
Even in your example, English is a given.
I stand my ground, you've made my case.