You can carry a jingle bell, but only deply it when you approach someone.
Personally, I HATE it when bicyclists or runners say "On your left" etc., because I know damn well they're approaching. When I was bicycling, I took total responsibility for passing safely, and I seldom asked anything of others unless they were providing me with no option whatsoever. And, after commuting and trailing in five major cities, I *never* hit anyone and never even startled anyone off a trail.

