I've seen the changes here in Southern California. The part of town I live in was for many years a white bread middle class neighborhood. A number of Mexican families have moved in the area and the standard seems to be at least two families living in the same house, too many dogs, junk automobiles parked in the driveway or yard, landscaping that doesn't fit in with the rest of the community, children running wild and Mexican polka music played at loud volume.
I keep code enforcement busy.
About half of the fast food restaurants and service stations where I live are staffed by illegals. In the poorer areas that really look like Mexico or South America the people won't even speak English to you or the police or other officials.