Mexico's fertility rate is down to replacement level and the country won't be sending more.
Guatemala is packing 16MM people into a place the size of Maine, half of it malarial jungle and half volcanic mountaintop. The fertility rate is 4.0, setting population to double every generation. Honduras and El Salvador aren't far behind. Those Central American countries are desperately poor with illiterate majorities, the world's highest murder rates, and low educational attainment. Nearly half of Guatemalans don't even speak fluent Spanish.
Meanwhile Mexico is a well educated nation on the verge of first world incomes.
So the quality of migrants is not looking up. But the quantity certainly is.