As it turns out there are now seven "Share the Road" signs on Killarney Way going east from Thomasville Road to Shamrock Drive. There are seven more going west from Shamrock Drive back to Thomasville Road. The signs aren't evenly spaced, but I managed to crack the code--there is a sign after each side street to the right. That is, a sign each after Thomasville Road, Limerick, Longford, Kilkenny, Tullamore, Raymond Diehl, and Foley going east, and a sign each after Shamrock, Killarney Plaza, Forsythe, Clare, Clare, Monaghan, and Monaghan going west. An enormous bicycle icon in reflective white paint looms on the pavement next to each sign.
That's a lot of signs on a 1.4-mile stretch of road, enough so that it's nearly impossible to drive any distance on Killarney Way without passing at least one of the signs. Beyond Killarney Way on the east, there are no "Share the Road" signs on Shamrock Drive, so I suppose drivers might feel free to bully cyclists; there is a similar lack of signs past the west end of Killarney on Maclay Road. Fortunately, in my experience automobile drivers on Shamrock and Maclay have been civilized enough to share the road without being prompted.
A bike lane might have been more effective, but the signs certainly can't hurt. Killarney Way is wide enough for bicyclists and motorists to coexist, so maybe we'll be able to share the road.