I take offense of the implication that the bicyclist should take full responsibility. It is a MUP, Multi Use Path. Like most things in life, if you choose to use it, you must take some responsibility, regardless if you are the bicyclist or the Ped.
The common notification is "on your left". If you have used a MUP, you have heard it. What question is there about it? You have also heard bells. What they often do is get someone's attention who often turns to look (the good). If they are tuned into their Ixxx then they won't hear you (the bad) as they wander all over the path.
My experience with the Crane bell is about 50% effective on people (not kids) for a number of reasons. Doesn't work on cars. If $50 is too much for a bell, use it to buy the
HORNIT. 120 db of high frequency, ear-piercing sound. Everyone nearby will look and be witness to the idiot behavior of the person you are focused on, car driver or ped.