I would also love to find out about purchasing a bus card for many journeys. I thought the bus service in Ibiza last summer was excellent. It only cost 3 euros to travel from San Antonio station to Ibiza town's main terminal station. The buses were very clean, air-conditioned, and there always seemed to be a bus coming or going. If the queue was too long for one bus, I just sat down and chilled, and before long another one would arrive. It's a shame the drivers don't say much. I think they were annoyed about the new station in Ibiza town. It had just opened when I arrived.