We’re from the SF area. We found it easiest to fly Norwegian (which has even more flights from LA than SF). Really cheap non-stop flights, which can be booked just as cheaply one-way as round-trip. For getting to St. Jean, you could fly non-stop to either Paris or Barcelona. (I don’t think they go non-stop to Madrid). If you go to Paris, you can then take the train (high speed TGV) down to Bayonne, and then transfer to the local train to St. Jean. Alternately, you could fly from the Paris airport to Biarritz (multiple airlines make the run), then pick up the Express Bouricot shuttle directly to St. Jean. (We found it easiest to stay the night in Paris, recover a little from the long flight, then take one of the frequent trains from Gare Montparnasse to Bayonne — but we’ve done it the other way — by air — too).
If you fly to Barcelona, you can take either a train or bus to Pamplona, where you transfer to another bus for St. Jean. Check the web sites for ALSA (bus) and RENFE (train) for schedules.
You can come back in reverse, getting yourself back to either Barcelona or Paris, then hooking up with the Norwegian flight to LA.. From the eastern half of the Camino, which is where you’ll still be after 2 weeks, it’s probably easier to get back to Barcelona, as there will be buses / trains from all the major towns. Most likely, you’ll wind up somewhere between Logrono and Burgos, and from either of. those cities, getting to Barcelona for your return flight will be easier than getting to Paris.
Note that on Norwegian, you just book your going and returning legs separately, so you don’t have to worry about an “open-jaw” ticket to book into one city (Paris, say) and come back from another (Barcelona).
Many people on this forum will tell you to go to Madrid, but they don’t necessarily understand what it means to fly from the west coast. Unless you can find a non-stop to Madrid, go via Barcelona or Paris, and take advantage of the non-stop flights from LA. Much less hassle than changing planes.
If you do make it to Santiago, the easiest thing may actually be to return via London. Easyjet has a. partnership arrangement with Norwegian, so you can book both the Santiago - London leg (Easyjet) and the London - LA leg (Norwegian) together. That will probably be the fastest way back, because if you’re returning via Barcelona, you’re actually flying in the wrong direction.
You can send me a personal message if you want more details. We’ve done this 5 times from the west coast.