According to 2000 U.S. Census data, nearly 47 million people who live in the U.S. speak a language other than English at home.
How much?! WOW!
Then, of course, I got interested in other numbers. Those 47 people are a part of 281 million people of total USA population in 2000, according to Demographics of the United States Wikipedia article. There is even a handy chart of population growth.
The latest numbers of total USA population are a bit higher – 300,000,000 people, as of October 2006 (according to Wikipedia page about USA).