Boom is always a problem. Getting there and back by public transport is a real hassle as Idanha-a-Nova is right in the sticks.
It is something I find strange about an event that supposedly supports green issues. The amount of carbon monoxide that has to be emitted getting to the event must be huge, given that most people have to come by car or taxi from Caldas da Rainha.
The best way to get to Malaga will be to get a bus back to Lisbon and then another one to Seville. To get to Malaga from Portugal you really need to go through Seville.
alsa.es operate a daily service from Lisbon to Seville as follows:
LISBON Sete Rios SEVILLE 20:45 05:15 next day Malaga 08:00
Alternatively, if you can get a lift from Idanha to Caceres in Spain (+- 130km) you can get a bus from there to Seville.
alsa.es have at present two buses on this route daily as follows:
CACERES 04:25 SEVILLE 07:35 MALAGA 11:00
CACERES 11:30 SEVILLE 15:15 MALAGA 20:45
Timetables may, however, change for summer and you should check closer to the time. Note that Spanish time is 1 hour ahead of Portugal Time.
Train - There are not cheap nor quick links between Idanha, Lisbon, Seville and Malaga.
Personally, I strongly recommend the bus.
