On my favorite MUP ride (an 8-mile loop that I did twice today), I've discovered that it's most crowded in the first/last mile because of all the walkers who use the one-mile marker as their turnaround point. I end up going pretty slowly in that first mile, just to avoid people running and walking up the middle of the road (this, in spite of the many signs telling them to keep to the right). That and people with dogs on long leashes, and young children on scooters. I call out a lot in that stretch because of all the foot traffic -- they're often unpredictable, or walking three or four across and passing them would be hazardous.
I yell out "on your left" if the walkers ahead of me are in the middle of the road or heading into a leftward curve because they tend to cut inside to the left into my path. I know it's flatter in the middle of the road, and so easier to run and walk on. I know this because I used to walk this path a lot, and I would always walk in the middle, too, because it's flatter and my back would hurt if I walked to the right -- the incline of the road is not that steep, but after a few miles of the left leg walking a half inch higher than the right leg, it adds up, so I understand, but it still bugs me when I have to brake to avoid hitting an oncoming cyclist because there are walkers in the middle of the road. That's my passing lane, doggone it.
Tonight I called out to little kids on bikes, "Hold your line, baby!" and their moms smiled at me as I swung really wide of their children.
There was another little kid out there all by himself. I guess his parent was walking somewhere behind him, but the two times I encountered him, he was alone. And I'm talking about a seven- or eight-year-old boy on a little knobby-tired bike. The first time I came up on him, he was coming toward me and he was walking his bike. I slowed down and smiled at him. "Long ride, huh?" He smiled back at me and nodded. Later, I caught him again on my way back. He was back on his bike and I pulled up alongside him to check on him. He seemed okay, so I said, "You can do it. You're doing great. You've got about a quarter mile left to go." He smiled at me again. I have no idea where his parent was, though.
There was a three-year old who'd gotten loose from her mother, too. Mom was fifty yards behind her, carrying the scooter and calling ahead to her little girl to be careful as the little girl is running along. At least she was sort of on the right of the lane, but she was tiny and the sun was going down by then. I think the faster riders out there would have a hard time seeing her if they were coming around a curve -- she was shorter than the shrubbery along the side of the road. That's just so dangerous.
I wish the park had more safety patrols to enforce the "keep to the right" rule, and the "keep your dog on a short leash" rule, and especially the "this is not a playground so keep your kids in check" rule. Maybe a few reminders to the vehicles that come through, too, not to cut inside on curves because there are cyclists headed your way and they're often doing upwards of 15mph. (and occasionally, I'm one of them)
So yes, I call out if there is an obvious safety hazard in trying to pass the person in front of me, but otherwise, I just pass them as quickly as I can with as much space as is safe and practicable.
Roxy