With the world becoming increasingly global, paying attention to non-English speaking audiences is becoming more and more important. You don't even have to look beyond the United States, there are many domestic communities where other languages can be widely heard. In fact, English isn't even America's official language.
Because 55% of the internet is in English, it makes the most sense to adopt it as your site's main language. That does mean, however, you are still ignoring a lot of potential customers. Without looking abroad, New England and San Francisco are full of Chinese speakers, New York and California are full of Tagalog, Houston and Dallas have a lot of Vietnamese, Chicago with a lot of Polish, Detroit with Arabic and Seattle with Japanese speakers.
And really, why would you want to lessen your chances of doing business with them or even internationally when all you need to do is use a multilingual site?
The easiest way to do this without getting too technical is to use your URL to geotarget. You can build completely different versions of your site, something very common for businesses to do when opening in Japan. For example, www.mysite.com and www.mysite.jp. Another way to geotarget is by building those versions right into your main site's structure. For example, www.mysite.com/en/page for English and www.mysite.com/jp/page for Japanese.
Whatever the method you choose, relying on automated translations may leave you embarrassed, just ask Taco Bell about what happened to them recently in Japan. Seek a company that provides human translations, even better if they are able to change your site for you and provide ongoing assistance. Going multilingual is a simple task considering that it will help open your business to new communities or even countries of potential customers.