Yeah, I'd add not to carry the cash on you, but keep some in the hotel safe.
And by "fair amount" I mean probably 300€ or so. Enough to get to Madrid/Valencia and then work things out from there.
Again, the possibility is very remote that things get to that point, but it's looking like they are going to declare independence and there are lots of things that can go wrong. Say they try to take control of El Prat and then AENA would be forced to shut down the airport until the Spanish government can guarantee control.