What is the percent foreign-born

population in the US?
Are you including legals only?
Is this more or less than in previous years?

Try the US Census Bureau - http://www.census.gov/

Coming to America - The Census Bureau Discusses the Foreign Born (PDF Format.)

As far as I know, they count noses, not green cards, so illegals are included.

In case you’re having trouble with Adobe:

They show a bar chart with the following figures:
1850 - 10%
1870 - 14%
1890 - 15%
1910 - 15%
1930 - 12%
1950 - 07%
1970 - 05%
1990 - 08%
2000 - 10%