If you want to see Obama's bill on health care reform, click here (pdf document). It is 1017 pages long but probably shorter than a Harry Potter novel.
Section 401 on page 167 deals with a tax on individuals without acceptable health coverage. It amounts to 2.5% of annual of gross income. There is some legalese which you may wish to help translate into plain English. There are some exemptions for people paying this tax. They include non-resident aliens (i.e. Canadians visiting Disney World), US citizens living outside the country, and US citizens living in possessions of the United States such as Puerto Rico, Guam, and possibly the prison at Guantanamo Bay. I don't think this section means that illegal immigrants/ undocumented aliens are going to get free health care. They, like Canadians visiting Disney World, will need to pay out-of-pocket for their health care while in the US unless they hold insurance of some kind.
Here is a link to an explanation of the health care reform bill simplified from NowPublic.