If you are planning on traveling by train, check the Renfe website. They have revamped the fare structure and offer tickets earlier than they used to, at least for AVE trains. Today, feb. 10, you can buy tickets for travel through May 10.
May be even earlier than that. I bought one for 11 May today. Jonathan
Jonathan, what time did you buy that ticket? Could it have been already 11/5 in Spain? When I checked it was before 3:00 pm, PST, so before midnight the same day in Spain. Tickets for 11/5 were not available at that time. They are now, however.