First, let’s clarify the question a little:
Are you referring to “as a second language”?
Are you referring to a formal understanding of the grammar, of the “rules” of the language, or are you referring to a working knowledge, for understanding what is being said and a modest vocabulary for expressing oneself?
Are you assuming a business environment, a multi-national exchange and communication?
Since languages are learned best by young people, it is a good idea to be comfortable with English, since the language seems to have become a universal means of discourse in the 21st century, and any activity a young person grows into will use English. Today, mass media such as television actually makes learning English, especially colloquial or informal English, easier. In America, the tendency is to learn a foreign language in a formal academic setting, usually in high school or college: there is less emphasis on learning two language when young, unless a child grows up in a multicultural environment.