If you have a tight budget, flying to Madrid and then traveling to Granada by coach, train or sharing a car may be a good option (check also Tips for those traveling from Málaga).
Granada is 420 km away from Madrid. Motorway all the way, it is an easy road. The trip can be done comfortably in under 4 hours (speed is limited in Spain in motorways to 120km/h, radars fire at 130km/h).
ALSA provides a coach service from the Madrid Airport to Granada departing from Terminal 4 (AKA T4). A "gratis" shuttle links terminals 1, 2, 3, with T4. There are a more frequent service also running from the "Estación Sur" to Granada. You can reach that station by Metro (40-70min), city bus or taxi (20min).
Trains depart from Atocha Station that is located in the city center. A coach service connects Atocha to the airport (Exprés Aeropuerto). You can also reach Atocha by train ("RENFE Cercanias", departing from T4) changing trains at Chamartin or by Metro (departing from T4 and T2).
For more specific advice don't hesitate to get in touch with the organizers or the local Perl Monger groups via email or IRC (#yapceu, #barcelona.pm at irc.perl.org).
There would be some attenders from Madrid or near places driving their own cars to the conference that would happily give you a free ride or even host you in their homes if you plan to stay in Madrid for the night or even some days; or guide you through the city.
In order to maximize the outcome, add yourself on the following lists, including when you plan to arrive/leave and ensure that you are contactable:
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