One of the many things I'm learning and have learnt about the medieval era is that you really can't generalise across centuries and across geography, still less across "ruling classes". Quite a number of 12th century rulers in Europe, Byzantium and north Africa were quite able to read and write, and, as I've mentioned before, it seems some relatively low-class entertainers could read, too. I've singled out those areas just because I've been looking at them - there is bound to be a lot of information out there about other parts of the world and other social classes. On the other hand, quite a few clerics weren't literate at all. It is because of the 12th century ruling classes in Europe that we have as much European written material as we do, as it was either written for them directly or sponsored by them, and some was written by them. The "nobility" was far more fluid than you might think in what we now call Europe, certainly.
And just as a postscript - I've been looking at some of the legal documents issued by James I of Aragon (from 13th century). His provisions for ensuring that Muslim communities in his lands stayed relatively stable and protected even when he had defeated their own rulers (and thus brought their lands under his control) would be a salutory lesson in how to co-exist in Israel and Palestine. But it's only history, and no one takes lessons from that, do they?