I think this is a good idea. This address information can be incredibly useful for campaigns like this.
I do have a concern that only a small percentage of people may actually take the desired action. I don't think many people will be willing to display posters.
Here is a rough draft of another approach that I have been thinking about for some time.
Hello,
We are writing to express our concern about some activity that is taking place in your neighborhood. As you know, you live near a Kingdom Hall of Jehovah's Witnesses. This organization is known for actively going door to door and discussing the Bible. We support their right to do this, but are very concerned about one specific feature of this activity.
Like every religious organization, Jehovah's Witnesses have some members who have a history of pedophilia or other sexual offenses. Unlike other religions, they ask such members to go to people's doors as an identifying mark of their religion.
We feel this poses an unacceptable risk to the children and vulnerable members of your community. In protest of this policy, we are encouraging the people in your community to ask to be placed on the Jehovah's Witness "do not call list". This should reduce or even eliminate visits to your home. If they do come, you have the option of calling the police since you have a right to bar their visits to your home.
Enclosed you will find a post card addressed to the local Kingdom Hall. It requests that your address be added to their do not call list. It is already stamped. All you have to do is sign it and drop it in the mailbox.
Thank you.