Hi Tex. Okay, I've got a few minutes so let's see if I can help. This is of course assuming that you are a Malaga supporter and it's purely coincidence that the other team is Real Madrid, right?
Buying a ticket for any Malaga game is not an easy operation. They don't sell them through the internet nor over the phone. The only way to get one is to go to the stadium, although they also used to sell them at El Corte Ingles, a large store in Malaga city, but I'm not sure about that these days.
So it's straightforward up to now, but this is where the fun starts because you are arriving on Dec 21st. Even though the match is scheduled for Sunday 22nd, it may be brought forward to the Saturday for a variety of reasons. The problem is that we won't know until ten days before the game or less.
Assuming the date's ok, then you have to take into account that Malaga's stadium is being remodelled and currently only holds about 27,000 fans. There are nearly 17,000 season ticket holders (Those of us who have paid for our seats for the whole season in advance). That leaves roughly 10,000 tickets to go on general sale.
I don't think it will sell out quite frankly. Normally there's hardly a seat to be had at these games, but lately whenever there is an important match the owners of the club have the view that they will get more money in if they raise the prices to a high level, but the reverse happens because a lot less people are buying the tickets! The same way of thinking is applied here to golf courses, some restaurants etc. If they aren't getting as many people through the doors, they put the prices up to make up the difference and of course then more people stay away! Stupid mentality! Anyway, I digress....
There is an important game for us this week when Malaga take on Leeds United from England in the 3rd Round of a European competition. The cheapest seat for this one if you are not a season ticket holder is 40 Euros and the dearest 100 Euros. I am guessing that these prices will be the same when Madrid and Barça come here, so be prepared to shell out high prices for a ticket.
So to sum up.... We won't know the exact date until around the 12th December. Prices for tickets will be high and the only way to get them will be from the ground itself, when they will go on sale four or five days before the game.
I hope this helps. In my view, I would think that you will be able to get your tickets on the day of the game, especially with it being the last one before Christmas. If you e-mail me nearer the date I will make enquiries at the ticket office to find out the hours they will be open that week. I'll meet you for the traditional pre-match San Miguels and fill you in on all the latest footie gossip.