I'm not in that part of CA, but just based on my recollection (from travels, etc...) of that stretch, and basic knowledge of the evolution of road systems and population growth here in CA, I would give the kill-joy view that any coin hunting (from old way-station stops, tollgate sites, etc...) is going to be nearly impossible.
Reasons are multiple: you are in a very VERY extreme growth region of the USA. Ie.: the southern CA/ Los Angeles area. Roads (4 or 6 lane freeways) you see now, were/are not necessarily the same roads (paths) that you see on maps of the 1800s. They got re-aligned (straightened, etc...) over the years of evolution as engineering progressed. And in that process, old turn-offs and pullouts were obliterated. Or..... if a stage stop or toll-gate were at the bottom of the grades in nice convenient flat spots, odds are, they are under a modern shopping center, suburbia, etc.... because people, just as back then, tended to develope in the most convenient flat spots.
That's one of the minuses of detecting in big cities, as opposed to rural areas. You are less likely to find a ruin (reminiscient of something out of a Clint Eastwood Spaghetti western movie) as someone in a rural area/state would find). That's not to say you can't find old coins, but you will tend to get them in urban demo's of some sort, not out in a cow-pasture, so-to-speak.
As far as nuggets, I can't speak on that, as that's a venue I'm not into.