I guess peds in Fort Collins are pretty bike aware. I use the "ON YOUR LEFT" signal and they almost invariably seem to get it. The only issues I've had have been with people either not comprehending the words or not hearing at all.

Oh, and once I had a lady jogger off to the right of the paved trail so I didn't bother to signal; she suddenlyy darted onto the paved trail just as I passed, and got pissed at me for passing so close to her!
Lesson learned; I signal also to people that are off the trail but close to it, when they aren't looking at me.