I’ve been riding the Cedar River Trail as part of one of my training circuits for several years now. Only on warm sunny afternoons is there very much traffic, either pedestrian or bike. Most of the time I have the trail virtually to myself. So I can’t imagine they are going to have a speed cop out there very often, unless there are complaints or something.
Two alternates I now take if I can, because I find the Cedar River Trail to be a little boring actually: One is Jones Road although it is a little difficult to connect out at 196th. The other is to go up 140th to Fairwood instead of going in to Renton. It’s a better climb anyway.
Instead of “on your left,” I have invested in warning bells for my bikes. They have been around for years and are actually required some places. It seems to me that people hear and understand a pleasant little bell and are quite happy to step aside. I never liked yelling “on your left” at people, many don’t really know what you mean or what it is they are supposed to do.
By the way, they have painted a dashed line down the middle of the trail. I find it helpful when practicing my time trial because I can now just keep my head down and not constantly have to look ahead. Much more aero!