Camino de Santiago

You may do better on a dedicated Camino blog or site. There are a number of FB groups that only deal with the Camino.

Edited: I did a quick look and there are a few bus companies that will get you there. Check the www.rome2rio.com website. Also read the following. From San Sebastián: Take a Euskotren (local train service) to Hendaye (just on the other side of the French border. Then take a train to Bayonne and then another train to St Jean Pied de Port. This sounds difficult but all parts of the trip are short.

Both times I walked the Camino I flew into Barcelona. From Barcelona it's an easy train to Pamplona and then bus to SJPDP.

But if you're locked into San Sebastian, there's a way to get to the Camino from anywhere. There are plenty of options.
As they say on the Camino, "The Camino provides".

(You will have to research the trip times and costs, I'm commenting from memory...)

Suggestions from San Sebastian:
Take a bus to Bayonne and then a train to St Jean Pied de Port. The entire trip takes about 2 hours. Approx 60E?

Its possible to take an SNCF bus service that takes the same route, but the trip by bus takes about 4 hours. I don't remember the price but I want to say approx. 60E
Also there's an ALSA bus that goes San Sebastian > Pamplona > SJPDP but it also takes about 4 hours.

I've also heard of Peregrinos taking a taxi all the way from San Sebastian (1 HR), but that will run approx 200E. If you share with a few others going to SJPDP that might be an option. Look for other travelers carrying backpacks and hiking poles...

The cheapest option would be by train all the way San Sebastian > Hendaye > SJPDP, but I'm not familiar with that schedule (or not sure you could do it all in one day).

Hope this helps and Buen Camino!

Two years ago I took a train between Bayonne and St Jean Pied du Port and a bus between Bayonne and San Sebastian. All pretty easy.

If you haven't already found them you should search for some of the Camino websites. Tons of useful information on them, lots of blogs as well.

I just walked from St Jean to Santiago in June - July last summer. From San Sebastian there is no direct route to SJPP. You can take an ALTA bus all the way but you'll have to change in Pamplona - that takes about 4 hours. OR you can take a bus to Bayonne and then take a train to SJPP - that's about 3 hours. The third option is to take a train to Hendaye, change to Bayonne, then change to SJPP - this method is the fastest.
Buen Camino!