My first four international trips were without a functioning phone, I had a smart phone along that only worked when I had wifi. I did not buy a local sim card.

My trip last summer was the first time I have actually used a cell phone in a foreign country with a functional cell phone plan. That said, I think the only time I used it was for weather forecasts or to check e-mail. When not in use, it was off.

I am sure there is better cell phone coverage on this route now than a decade ago, there were two of us with different phone plans. Sometimes mine worked, sometimes my touring partner had a phone that worked. About a quarter of the time, neither worked. Once when neither phone worked, I made a call using my smartphone with restaurant wifi. And once we needed to make a phone call and we actually found a pay phone, remember those?

There have been more frequent forest fires after I did the Pacific Coast route, so you might need to check daily just to see if there are any fires further along the route that you need to worry about. I do not know if there is a "best" web site to check. This might be the best one?
https://www.airnow.gov/wildfires/

I thought the book I had on this route had benefit, it helped here and there telling us bits of info that was useful at the time.

When backpacking, I will be much more careful about weight. I have cut the spine of a book with a utility knife to only carry the pertinent pages for my trip. But bike touring, I do not mind some additional weight, the weight is on my tires, not on my feet. I do not carry canned food or a glass wine bottle on a backpacking trip, but have carried both on a bike trip.

I had great weather when I was there, you can't beat this: