FROM Census web site:
People QuickFacts Los Angeles County Population, 2005 estimate 9,935,475 Population, 2000 9,519,338
Also, with respect to the post that LA COunty has 34,000 square miles, here, from Wikipedia: Area - Total 12,308 km² (4,752 mi²)
However, your official census figures are way off. Ask the city.
The main point remains unaddressed: No one knows how many illegal aliens there are in LA or anywhere else. If you think it's around 10%, go take a look. Or sit in an elementary classroom in Santa Monica.