I know if it were me, it would depend on what type of "relationship" I had with the neighbor. If it was someone I wave to on an almost daily basis, and have had conversations with at one time or another, then yes. I would tell them of my concerns and why it might be safer riding on the correct side of the road.

If it was a neighbor that I never wave to and have never spoken with except once or twice, then no. I would say nothing as it might be misinterpreted and create animosity.

But that's just me. And I am not known for being the nicest person on the block.