As noted on the McDonalds Spain site, the McRib has again returned. This time the McRib is featured as part of their McMenu Easy promotion. From my interpretation of the promotion, this is similar to the Dollar Menu concept here in the United States, however has been expanded to include a select few value meals.
The McRib will remain on the menu in Spain through April 30, having actually started April 2nd.
Thank you James Frewin for reporting your sighting in Spain and tipping us off to the McRib availability!