Searching4, my friend in town has the same experience. She's a stay-at-home mom in a nicer neighbourhood, and she NEVER sees witnesses walking the beat, for at least five years. Now that she's invested so much research, she's been eager to test it out on a JW. I suggested she try out the local doughnut shop. She speculated that the local wealthy witnesses may prefer to schmooze with their weathy friends at bbq's and such.
A sure-fire way to get someone to your door is to fill in the Contact Us form at the www.watchtower.org site.