The numbers from the 2010 Census rank California cities like this:
Los Angeles: 3,792,621
San Diego: 1,307,402
San Jose, 945,942
San Francisco: 805,235
Los Angeles actually grew by 2.6 percent since the 2000 Census, but the official count is well below the state's 2010 estimate of 4,094,764. The real number of humans living in Los Angeles is probably closer to the bigger figure, but the Census is what we have — as well as the closest thing to a physical count.
Fresno had the fastest growth rate — 15.7 percent — and Los Angeles the slowest at 2.6 percent. Here's how the 2010 Census ranks the top counties in California:
Los Angeles: 9,818,605
San Diego: 3,095,313
San Bernardino: 2,035,210
Notice that's 20 million residents of Southern California without even counting Ventura or Imperial counties [or Santa Barbara if you're so inclined.]
Here's Mark's take at LA Biz Observed. We'll both have more as we get time to poke around in the tables.
* Map added after the jump: Counties by total population. In this case, greener is bigger.