Don,
Dawah can be done within muslims also, I beleive, though not sure about the technical terms. Ever been to the markaz in industrial area? It is a majid, a very big one indeed. There are classes in many languages especially on Thursdays & Fridays. You never noticed tableegi jamats coming to your neighbourhood masjids? Don't know about the ban...just sharing my understanding (been there in the past)..