It seems to me that if one were really dedicated to missionary activity, one would learn the language of the target country FIRST. Surely there are lots of places in the world where English speaking people live in sin and such.
I was staying at a sort of backpacker's farm in Paraguay, the Granja El Roble (paraguay.ch) and we were visited by a couple of girl Witnesses from Germany. Being as they came on bicycles and there were a dozen lost non-Witnesses, they stuck around. Apparently there is no real reason why Witness Kingdom Halls are windowless, and why they brick up the windows of buildings they repurpose as Kingdom Halls, as opposed to simply using curtains.
They claimed that it seemed entirely logical that Germans should proselytize in Paraguay, but not at all logical that Paraguayans should proselytize in Germany. The sect began, of course, in the USA. They claimed that they had never met anyone who questioned that the Bible might not be the word of God. They did not get into what happens when only one member of a family becomes a Witness (he is encouraged to separate himself from non-Witnesses). And of course, neither of them would consider reading the Book of Mormon.