Hi
Coming over for a lifetime road trip from UK in October
Some of our stops:
Sausalito - (we will be touring around SF - i have high expectations )
Yosemite-( I'm guessing a short caffeine break?)
Napa
Monterey
San louis Obispo
West Hollywood
La Jolla

2 or 3 nights in each and mobile. So top quality cafes / roasters- the ones you would take your best friend from out of town to show off how good you've have it
In return, not only my eternal gratitude but the secret inside knowledgeable track if you ever need it in London

Since you are in West Hollywood, I would try "Toasted and Roasted". It's not directly in West Hollywood, but not far away on Melrose Ave. Small roaster, that roasts their beans in the shop.

If you make your way to Culver City I also like " The Conservatory for Coffee, Tea and Cocoa".

But of course we are talking about LA which has probably hundreds of shop. I personally like and support the smaller once that only have one location.

Thanks
Personally i enjoy supporting small businesses that take pride in a great product.

I had excellent coffee - though not as espresso - from Ohm roasters in Napa a few weeks ago. (Jax Mule diner in Napa. Get the beignets for with.)

Copa Vida in La Jolla would be a great stop. If you're passing through Santa Cruz to Monterey, I'd recommend stopping by Cat & Cloud.

Acme in Seaside (Monterey).

Acme is good, on the dark side IIRC, and they pull with a lever. Check the hours because they close by 3:30 most days.

I like Red Bee Coffee in Grover Beach for coffee when I'm in the area.
Spearhead Coffee in Paso Robles is good too.

I tend to avoid the parking hassle for the shops in San Luis Obispo and visit these small shops in the small cities nearby.

It's funny, I just had some friends from the UK stop by on their way from an LA to Vancouver road trip. Not sure if Santa Cruz is too out of your way, but anyway we decided on Cat & Cloud which always has great vibes... but their coffee (The Answer and a SO Kenyan) was noticeably grassy and vaguely sweet. My friends didn't seem to mind but to me it was distracting. Their coffee has been hit or miss but their shops are worth visiting. Their shop on Front Street is adjacent to lots of food options which is a bonus.

San Francisco:

• Andytown is great and within walking distance of the beach. The standard drinks are good, but they also have the snowy plover which is a lightly sweetened espresso with carbonated water and whipped cream.
• Linea cafe, Ritual, and countless others are great as well.
• There is a Fellow store where you can go in and see all of their products. You can also by a dose of beans and use their equipment to make your coffee.

On the way to Monterrey:

• Chromatic in Santa Clara / San Jose
• Cat and Cloud in Santa Cruz

La Jolla:

• Bird Rock is great. One of the best cortados I've ever had.

SF:
Verve (IMHO the best roaster in the area, although their Santa Cruz cafes are a little prettier than their SF location).
Andytown I adore Michael/Lauren and they have a Kees Lever, but I find their coffees a hair too roasty for my taste. That said, their house-made baked goods are incredible. They make the only muffin in the world I get excited thinking about.
The Mill & Sightglass (on 7th) while both are very passable third wave coffee shops, they are two of the prettiest spaces in the city. The Mill is also the home of Josey Baker Bread which is fantastic and does some innovative things with sourdough. Perhaps finally try that $8 avocado toast you've been hearing so much about .
Mazarine Coffee a multiroaster in a very pretty space downtown that has great food.

Also I am going to throw out Tartine Manufactuary, I know they roast now, but I've never had their coffee and can't vouch for it. That said, It's an absolutely stunning space and their breads/pastries have won James Beard awards. The rest of their food is on par. Also don't forget to stop by Heath Ceramics nextdoor (or in Sausalito) to pick up some beautiful demitasses.