As a resident of #1, I can say that we are not teeming with refugees or Central American residents. They tend to reside even farther from DC or in independent VA cities within the county, which are not governed by the county or included in county stats. We do have scores of H1B visa residents and my home is somewhere on the border with New India, West Pakistan, and oddly North Kenya.
I know Montgomery County MD, extremely well. You can drive down Rockville Pike to Wheaton then take GA avenue and not see anything but 3rd worlders. No white people at all. The east part of Montgomery Co might as well be another country.