Just hang a nice big DO NOT DISTURB or NO VISITORS WITHOUT INVITATION sign on your door, and put a NO TRESPASSING sign at the beginning of your driveway.
These serve as "fair warning" in legal terms and you can call the police on people who are not welcome. Call the cops once on the JWs, and I guarantee that they'll stop bugging you with Spontaneous? We-Were-In-The-Territory? visits.
I put a sign on my door that applies to various situations and it works very well. It says
NO SOLICITING
NO PEDDLING
NO PREACHING
That way, if JW family members visit (they don't, but just in case) they know they are welcome as long as they don't talk about their cult.
Love, Scully