42 people were injured in an ETA explosion in Madrid last year, and there were 3 deaths in 2003. It's true that few of their recent bombings have caused much damage, tho whether that's due to a decrease in activity or better policing, I wouldn't like to say. There are persistent press rumours of an imminent ceasefire on their part.
The Camino would be a good target for terrorists, as it's an important part of the local tourist industry.
Peaceable Projects Inc. is a U.S.-based non-profit group that brings the vast resources of the wide world together with the ongoing needs of the people who live, work, and travel on the Camino de Santiago pilgrim trail network in Spain.