I think that the dates of your travel are quite O.K. As Albert says, Holy
Week and Easter Week spreads from the 14th of April to the 30th of April,
including a Bank Holiday on the 1st of May (and the 2nd of May is also
holiday in Madrid). Expect plenty of people everywhere during this time
of the year in Spain. If we are lucky and still have some snow, there
will be people at the ski resorts, but most of the people will be heading
to the beaches or to places like Paris or London. So you come here just
before the frenzy. Not so many people go out the couple of weekends before
Holy Week (you have to save some money...).
I would try to book accomodations as early as possible with places like Barcelona or Bilbao. I have a couple of hotel recommendations for Jaca. I must look for the numbers. My friends usually go to the Conde Aznar, small, they say that the breakfast is good to get down the slopes. Regarding Bilbao, there are a couple of new hotels that I should have a look. Just one question, do you intend to drop your car in Bilbao, or do you think about driving to Madrid? In this last case, we should look for a hotel with parking facilities.
About the ceasefire and the whole shebang... Well, we havenīt seen much of a difference in the environment, really. Except that right now is raining as if it hadnīt rained before. Traveller beware. Just as long as you donīt get yourself lost in the radical haunts (and weīll try not to get you lost), and itīs not normal to go through them. The targets are mainly politicians and members of the so-called spanish parties, and of course, there is a low-key violence that has always been there, and itīs the same in every country. Disenchanted youth, lack of employment, lack of prospectives, they can choose to be basque radicals in the Basque Country or right-wingers in Germany or soccer hooligans in the U.K. Itīs really the same, when you look at it.
About El Bulli. I havenīt been there myself, but I have friends that have been there. They say that itīs a very modern cuisine, lots of deconstructivism, of course pretty daring and very expensive. Although they wouldnīt have missed it. The chef, Ferran Adriá, is a bit of a star in Spain, not so popular as some of the basque cooks like Argiņano, Arzak or Berasategui, but well-known. If you are interested in traditional with a modern twist cuisine, I could find a couple of places in Bilbao.
And now I must get back to work and also try to begin with my travelogue to Vienna. It seems ages, and I came back just last week. Cheers. Covadonga in Bilbao