Check out this website I found at pewinternet.org
Eighty-five percent of Americans age 18 and older own a cell phone, and one-third (33%) of those who do not own a cell phone live in a household with at least one working mobile phone. This means that overall, overall, 90% of all adults live in a household with at least one working cell phone.
These findings are based on a survey of 3,001 American adults (ages 18 and older) conducted between August 9 and September 13, 2010. The margin of error is +/- 3 percentage points. Interviews were conducted in English and Spanish, and the survey included 1,000 cell phone interviews.