Iowa caucuses are precinct-by-precinct. Only in a very few places would those from outside the precinct not stick out like a Klansman at a NAACP convention.
In Republican caucuses, it’s unusual for there to be more than a few faces that aren’t recognized, even in large suburban precincts.
Hillbuzz has a different take on the democrat side. Read w/ caution:
http://hillbuzz.org/the-iowa-caucus-picking-presidential-candidates-through-chaos-and-ineptitude-60413