It seems challenging to get to San Sebastian from Biarritz and spend a long day there!
I would like to take a cooking class there and need to get there for most of the day....
The buses dont seem to have a very frequent schedule (www.pesa) and the trains seem confusing. From Biarritz ,La Negresse. to Hendaye then Euskotren to San Sebastian. Some say that the train from Hendaye can be a very long wait , any thoughts ?

Forget the train! I took the bus at 9 AM and came back at 6:45PM.Easy short ride.

The other disadvantage of the train is that the station is on the outer fringe of Biarritz while the bus stops in the centre. The bus company is PESA. Last time I looked there were two buses daily but that may have changed.

Some say that the train from Hendaye can be a very long wait , any thoughts ?

From Hendaye the Trein Eskro runs very frequently - kind of like a commuter train - take a bus to Hendaye from Biarritz then the train if bus schedules the whole way are not running at the right time for you.

The wait for trains at Hendaye thingy probably comes from if wanting to go by mainline train from Hendaye to Donsotia - the preferred name of San Sebastian to Basques - there can be long gaps between trains from Irun/Hendaye - border stations to San Sebastian's mainline station. So either take a direct bus or bus and Tren Eskro.

I think that the train that PalenQ mentions is actually spelled Eusko Tren. It departs from a small station about 50 yards to the right as you walk out of the SNCF station in Hendaye, and arrives at a small station in San Sebastion about a mile from the RENFE station. Trains run about every 30 minutes and take about half an hour. It is cheap, something like a city tram car, and has beautiful classical music piped in. There are many buses coming and going from the Hendaye SNCF station so I would expect that a bus from Biarritz would land you there.

Thankyou all for the info. It seems the bus route is easiest. Which bus was it ?
I didnt see the one Chapla mentioned on the pesa site .

The Euskotren station is indeed a short walk from the Hendaye SNCF gare. I took a picture of the distance here

When I took it last I got off right at the Hendaye train station - right onto a platform of the station.