I am not a trail runner but I feel bad and not sure if this is common. I always leave one ear phone out and sometimes don't wear at all. I've screamed in fright a few times at trail runners who have startled me. I scare them back and I feel so bad. The other day it was silence just birds then stomping behind me. As I screamed he was just saying 'on your left' they do try to announce themselves but even the sudden announcement can make me jump.
I feel this is not normal especially after typing it out! My walks I do mentally detach myself. I rarely see anyone as I stick to very early weekday mornings
If you don’t want to drive somewhere else, as mentioned already the top of the hill behind the Albertsons on Los Serranos has a pretty good view of multiple firework shows to the north and east. I went there last year and there were multiple groups there, but not too crowded.
https://maps.app.goo.gl/gvLB2Qx9T4vibhUG8
4th of July Fireworks
ChinoHills