Speakers will be staying in the Hotel Palaceio de Aiete.
For those flying to Spain, you will be arriving in the Bilbao Airport. Once you are on the ground, you will take PESA bus 50 to Donostia-San Sebastian. The bus picks up on the lower level of the airport (where you will exit after picking up your bags). It leaves every hour at the 45 minute mark and costs 16.85 euros. It will drop you off at the “Pio 12” bus station, at which point you should take a taxi to the hotel (there will be a taxi rank at the bus stop). The taxi should not be more than 10 euros.
Here is what the airport PESA bus looks like:
There is space beneath the bus for your bags and it is about an hour from Bilbao to San Sebastian.
To return to Bilbao airport, buses leave every hour on the hour starting at 5 am from the station at Pio XII, where they drop you off. The PESA timetable can be checked here. Note that the route you take is between San Sebastian and Aeropuerto Loiu (NOT Bilbao, which will go to the city).
The venue (Casa de la Paz y los Derechos Humanos in Aiete park) is a short walking distance from the hotel; there are a variety of ways to walk there in less than ten minutes. Here is one option: