Yes, I've counted those I see in my little town and then nultiplied. I figure my method is as good as any government stats. Also I remember 86 where government stats said 1 million would recieve amnesty and 3 to 4 million did, so I think something similar will happen again, gov says 11 million you can bet the real numbers is two to three times bigger.
IOW, your stats are no better than anybody else's -- it's just an extrapolation from a single point. It may well be more than 11 million illegals, but I suspect your number is at least partly informed by a personal desire that it be more than the gov't says it is.