According to repeaterbook.com, there are 233 repeaters within a 25 mile radius of 95037. There will always be dead spots depending on terrain and frequency
Exactly. They're all down in the valley with some good ones on the high peaks to the west. The one that I know of on the east side has a direction antenna that, you guessed it, points down to the valley.
Now look up the terrain. The state park is to the east. It starts at 2600' and descends from there. It's 100000 acres of ridiculously steep terrain. I can hit repeaters from all the peaks and none of the valleys. On an average 4 hour ride I never see another soul.
If I happen to get bit by a rattlesnake or get a compound fracture on a peak, I'd be able to call in the cavalry. In a valley, I'd be dead.
HF on a mountain bike? Nope.
855.4875 Mhz is my friend, CA state parks "green". It's still not 100%, but about 90%.
It's my long-term goal to develop a map of places in the park where I can hit a repeater with an HT with a good antenna. I usually have a bunch of other things to do when I'm out there so it falls off the priority list.