I long ago stopped using 'on your left' or anything similar because too many people moved to their left. A bell seems to do a better job of letting people know I'm behind them and they're now expecting to be passed on their left.

I think low volume MUPs can be great facilities if every user obeys some simple rules like keep right except to pass (or at least move right when there are conflicts) and bicycle riders are considerate of people who are walking. There was some debate here a few years ago with runners and some walkers wanting to do so on the left which was causing a lot of conflicts. Today everyone keeps right and everyone seems quite happy. When traffic volumes increase then it's time for separate facilities for bicycling and walking.