I’ve kept the opening as close to the original as possible. Throughout 
the story, there are references to listening, hearing, telling, speaking, recounting – but only very few to reading and writing, and none of those in connection with the story itself. It is probable that the story was told from memory, rather than read from a book, and it certainly was never intended for silent reading in an academic study!
I’m fascinated by the narrator claiming to have heard this story from “a foreign knight, a relative of Arthur and Gawain”. As it seems quite possible that Leonor’s family came to visit her in Aragon, it is quite possible that this claim was true, but even if not, it would have sounded convincing to an audience.
For those who like to know: Arthur in Occitan is Artus, Gawain is Galvan, and Kay is Qex. I’m intrigued by the apple branch/baton as a sign of Kay’s official position. Carduel is possibly Carlisle, but none of the geography of the tale is realistic.
There is a mosaic in the cathedral of Otranto which shows Arthur riding on a horned beast. It’s possible this introductory story comes from the same source. 
A lot of scholarship has been undertaken to suggest various deeper meanings to this story, and how it might act as a metaphor for all sorts of things. My experience of telling the story suggests that it is a piece of entertainment to get the audience listening to the story, and the action moves on so quickly it’s difficult to spend long considering the implications. I think it’s important that Arthur finds the whole adventure funny himself.
Arthur’s queen is called Guilalmier here, not Guenevere.
The name Jaufre is Geoffrey in its anglicised form. It’s worth mentioning that Leonor’s uncle Geoffrey/Jaufre of Brittany is called Jaufre by the troubadours, and associated with the forest of Bresilianda (Broceliande), and had a son called Arthur. There is also her great-grandfather, Geoffrey of Anjou, who gave his name to the Plantagenets, and there is the famous story that the name came from his wearing a broom flower in his helmet – and so Jaufre’s garland of bright flowers may be a reference to this. The description of Jaufre is very similar to descriptions of Geoffrey of Anjou and to Richard Coeur de Lion (another uncle of Leonor’s), as well as being a fairly standard heroic description.