What chinese language could be Wukong's first learned language (Mandarin, Wu, ...)? His native language must surely be the language of the Rhesus Macaque's, but what human language did he learn first? What other human languages beside Chinese dialects/languages can he speak? What animal or monster (dragons, demons, ...) languages can he speak?
I show in this article that Monkey was born around the year 500 BCE during the Zhou dynasty. (This is of course a rough estimate and should not be taken as gospel considering that the novel doesn't follow a strict historical timeline.) He is roughly 320-years-old when he sets out from the Mountain of Flowers and Fruit to find a Buddha, Sage, or Immortal to teach him the secret of escaping Yama's hand (i.e. death). This would put his arrival in the Southern Jambudvipa continent (China) around 180 BCE, during the Han Dynasty. According to Wikipedia, "late Old Chinese" was the language of the day:
https://www.youtube.com/watch?v=zyaFKnUumAM
But it should be remembered that Chinese changed by the time Wukong was released from under the mountain around the year 640 CE. The language at this time was "Middle Chinese":
https://www.youtube.com/watch?v=OX047xj6HtQ
But we’re being way too literal here. The Journey to the West (1592) was written during the Ming dynasty, so all the characters are speaking Mandarin.
Regarding your question about other world languages, the problem with the novel is that it falls prey to "provincialism", meaning that no matter how far the pilgrims travel outside of China, foreigners always dress and speak just like the Chinese. This is likely the result of the author-compiler not knowing much about the world outside of the Middle Kingdom. Because of this, Sun Wukong wouldn't need to know any other language than Chinese. Of course, this would be different in our world.
Monkey doesn't seem to have any problem communicating with other magical animals or gods, spirits, demons, etc. I'm assuming the "universal language" of all magic beings in the book is Chinese.
