pardon me if this isn't where it's supposed to be...

Google will be your best friend. We've also always found a CG along the coast from San Diego to the Can/US border. If you don't have a mifi hotspot, you would do well to get one. We use Verizon and can look into CGs while on a trip if needed. DW pre-books every single CG on our trips to make sure we aren't left in the lurch. Some CGs are fully booked weeks to months in advance.

If you think 101 is hard, try along the I-5 corridor...