Hi there!
Do many not come up as available just because it's too far in the future?
That's probably right. I know a lot of the hostels (called "hostales" in Spanish - "hostals" is a Catalán word and otherwise doesn't exist in Spanish or English - these are budget hotels and shouldn't be confused with YOUTH hostels) won't accept reservations more than 3-months in advance. Probably better to wait 2-4 months beforehand and try again and you'll likely have better luck.
Anyone have any other websites to check or have personal recommendations of good private hostals near central Madrid?
Errr... How about THIS one? You'll find LOTS of reviews about most of the hostels and hotels in Madrid, Barcelona, Seville, San Sebastián, Santiago de Compostela, and.... errr... MORE! Just type the name of the establishment PLUS the city name into the search function for this forum category and you'll likely find these reviews.
Maybe websites direct to the hostals instead of using hostels.com.
Hmmm.. Let me think... ummm... (heheehe...

) how about MadridMan's Madrid Hostels page @
http://www.MadridMan.com/madridhostels.html ?! There, you'll find a link to EVERY hostel in Madrid which has a website (I think there are nearly 150 by now).
I always recommend booking DIRECTLY with the establishment itself. Through them, you'll know for sure exactly how many rooms they have available, you'll pay no extra fees, and no cancellation charges (unless you don't show up or don't cancel within 24-hours in most cases).
Good luck! Saludos, MadridMan
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