Check the Bancotel website @ http://www.bancotel.com/ for coupon booklets for hotel discounts. You'll find MANY MANY reviews about their service here in this forum category so conduct a SEARCH to find them.

Otherwise, most all hostels (called "hostales" in Spanish) and pensions (called "pensiones") are much cheaper than hotels and in many cases are adequate for travelers.

High season usually include Easter week as well as the summer months until the first week(s) of September. Some hotels/hostels have seasonal prices and others don't - just depends.

Good luck! Saludos, MadridMan