Most realistic estimates in 2006-2007 started at 12 million and went up to about 20 million, which seems more realistic.
No one with any common sense would say the numbers have gone down substantially since then.
By the way, I had a real shocker last November/December while assisting a disabled and elderly acquaintance to the local Social Security and state medical offices here in Northern Virginia.
On a couple occasions we were the only native Americans in the offices (which were crowded), and on every visit the crowd was at least 85 to 95 percent Hispanic, most of whom appeared to be Central American peasants.
... and we veterans go to the State Employment Offices and we’ll be the only one in line who speaks English.