I recall in 1993 when he said the same thing about illegal Mexicans and NAFTA. Boy, that sure worked out, didn't it....Might I propose that those are actually people from the Dominican Republic, Guatemala, El Salvador, Honduras, Nicaragua and Costa Rica making their way through Mexico into the US?
Weak, I know, but logical and possible ...
Actually, there are lots of people from those countries you mention, but also, LOTS of Mexicans, too.