I just did a 4000 mile AMTRAK trip in October and no one searches anything. By the way, to get from San Diego to SF you will change trains in LA
For obvious reasons, your carry on bags may be searched. Call AMTRACK and ask them if your stuff is allowed. If not send it home Via UPS or FED EX, the USPS. No chance of hastles or watching your stuff.
Amtrak does not search you or your bags.
No