A few comments.

> A blog post from 2014 (link below) talks about signaling on former SP coast line.

The first picture in that link isn't the SP, probably the AT&SF.

> He says the switches are hand throw. Is that the case for the entire coast line?

For the most part, yes, although there are several locations which have spring switches.

> Do both meeting trains have to come to a complete stop under the track warrant system?

Not if the one taking the siding is already in the siding with the switches lined back, and the train holding the main has an after the arrival of warrant (which are almost never issued these days). The same is true if the train holding the main is already there and has lined the other train into the siding. When engineer-only, all trains must stop whenever the E must copy a warrant.

> The blog also says that UP removed searchlight signals and a pole line from the line. Why did UP downgrade the signalling on this route? Cost savings?

Searchlight signals are relays, and thus are subject to the periodic testing requirements of the CFR/FRA.

> He shows a video of a meet at a place called Devon with Amtrak #11 waiting in the siding. I wonder if random meets on the coast line have a big impact on the Starlight's on-time performance?

If the DS is a poor planner, yes.

> Signal spacing was increased,

Yes, cuts down on maintenance -- fewer signals and relays to take care of.

> A few [ well I know of one] spring switches are available.

W/E Bradley, W/E Santa Margarita, Surf, Sudden, E/E Conception, etc.

> But to add to your question, Salinas had "poor man's CTC" for the siding. That is, the DS could set an auxiliary signal to indicate 'enter siding'.

This is called a "take siding" signal (or indicator) mounted below the signal head. It's a letter S which, when illuminated, instructs the crew to line themselves into the siding (Castroville is the nly one). Both siding switches are spring switches.

> I wish I knew when that was installed,

Most likely in the mid to late 1930s.

> and when/if it was removed.

Still there AFAIK.

> The Salinas valley ships out 90% of the lettuce consumed in America from April to November. Why not some kind of cold express operation out of Salinas?

The die-off of perishable traffic on the SP started in the latter 1980s. There is still cold express operation, it's called "18 wheelers", and these are either driven to a piggyback loading facility on the Santa Fe in the Valley or directly to the customer. One of the big problems in trying to resuscitate RR perishable traffic is the loss of unloading facilities at the destination: all those spur tracks were torn out long ago.