Always say it to pedestrians. Always have gotten a good response, the first person I did it too was a jogger and got like three feet off the path. I call out very early. The startled ones never seem to move left for me, they just jump and say "Oh my gosh." I've never passed a cyclist on an MUP, and only one on the road. No need to announce, I just took the lane as he was riding on a paved shoulder.