I was spotting in Zaragoza 2 years ago from outside. Stayed there for 3 hours and no problem with security
there are 2 runways as you surely know. In a normal day they use the main civil runway for take off and landing and may use the other one for t&go (especially for C130s).
My guess is that for the tigermeet they will use the old military platform and the old runway so you must find a good spot for that rwy. There is but not so good as in the other side of the airport the fence is far from the runway.
That day I do not needed to go there, they were using the main rwy, just went to see to find a spot and surely you can find one.
However the civilian part is really far from the military one and if they will use only that one, for sure you will see nothing there. Maybe only the based F18 could land there as the 15 ala is just on the right of the final part of the civilian rwy.
another problem in zaragoza is the sun.... in the morning you are against sun...
this is a picture taken at noon more or less with cropfactor 1,6 and 400mm lens from the spot over the hill at the landings of the civilian rwy
LEGZ_130722_2 by
Giampaolo Tonello, su Flickr
here you are in between of the 2 rwy (even if the military one startrs at the end of the civilian one) and could take shots of the C130 making t&go
LEGZ_130722_3 by
Giampaolo Tonello, su Flickr
as you see at noon you have the sun in the middle. From 2pm it gets better and better
LEGZ_130722_1 by
Giampaolo Tonello, su Flickr
this was taken at 2pm more or less but after I had to leave....
However if you have a look to google earth you may understand better....
ciao