Some have said to not ever let them in since that would be inviting darkness into one's home. Others say that evangelism should be extended to even them.
Frankly, one should never try to deal with them unless one is prepared...equipped with a good knowledge of their deeper beliefs, and to challenge those beliefs beliefs biblically.
Therein is the problem. The NWT (New World Translation of the JW's, which is no translation at all, but rather a paraphrase) and the various works of the LDS, such as Pearl of Great Price, Doctrines and Covenants, BOM, etc., even their paraphrase bible, it all is infused with error that helps to keep them from ever believing modern translations derived from the majority texts and the Dead Sea Scrolls, they are utterly bankrupt in their writings given that they have nothing better to go on than the more modern authorities in their respective religions.
So, no. Unless you're prepared and equipped, it will not go anywhere with them. I was LDS for about 12 years, so I'm well acquainted with their deeper beliefs. I've also studied JW-ism and have become quite adept at dispatching their misinterpretations and outright false parallels.
We are also mindful that anyone, and it means ANYONE, who brings forth any other Gospel than that which the apostles gave to us, they are to be accursed. That is indeed true of those cultists who refuse to hear the sound Gospel we have through the majority texts in our translations. They are accursed until they have that change of mind and heart.
MM