In Spanish speaking congregations in New England, we have to make a list of Spanish or Portuguese sounding names to call on. The Secretary and a helper draft up the lists and divide the names and addresses into territories. Call calling on non-listed households is very seldom called unless one knows for a fact that the householder is Latino or Spanish speaking.
Getting references from other Latinos in the community is one of the best ways of building lists of names. It used to be that phone books were the place to find Latinos. But not anymore, with the over abundance of mobile phones the land lines are dwindling.
Another way is to go to a Mexican Restaurant or other restaurant you know the kitchen crew is Latino, and make contact. Once you have a chance to make a visit on one of them you have a way in to get info on the whole group that works there and even other restaurants.