I wish I had an answer for you, but I doubt going around door to door and asking "are you undocumented and in need of assistance?" would get you anywhere. I would just try to find your local leftist group and see what they're like / if they're any good. Then maybe you guys can investigate conditions in your area and brainstorm ways of reaching out to people. We had decent luck with movie nights plus a discussion afterwards to introduce our organization to people.