Hi,
I have to agree with LEVC on this one.
I have never been denied a jumpseat with Spanair and Air Nostrum so far (i think it made it around 10 times +/-) but with Iberia most times had been denied.
Even to visit the cockpit and greet the crew (as I don't have the opportunity to fly I enjoy quite a lot spending a few minutes in the cockpit or jumpseating in an approach), from Spanair I always got at least the invitation to stay in Business Class (I don't mind flying flying in the back, but I mention it because is a detail of kindness and airmanship) from the cabin crew as well as a chat with the flight crew (or at least they told me to drop by after the flight). With Air Nostrum I got a somewhat special attention as well.
From Iberia, to be fair is a 50-50. Sometimes they even don't tell me anything, and some other times they do treat me really well. Although there's a bit of everything in all the company, the MD fleet crews are normally much friendlier, specially the flight crews. The reason may be that they're former Aviaco employees, and don't have so much arrogance as many of the pure Iberia-breed staff have. Some people (me included when I said I was flying a Bonanza as safety pilot) have been denied the jumpseat for flying "small artefacts" (happened as well to corporate pilots and instructors).
Anyway, my suggestion, as LEVC said, is just to drop by and ask for it. There's nothing left to loose.
Good luck and best regards,
Pablo