Unfortunately, as Monkey progresses throughout his journey, his habits do not progress in the right direction over time. In fact, one could argue that they get worse. In regards to Buddhism, Monkey King shows to the readers that he is full of desires. He wants and wants until he gets, and that part of his personality drives him forward until the end. This feeling of 'want' is a total opposite of what a Buddhist values, and Monkey has proven once again to stir from the path.
Buddhism is a religion based on the journey and achievement of Nirvana, or enlightenment. A Buddhist would not desire more than their basic needs, and one would not care for fame or recognition, for they poison the mind. One would cleanse itself from all other outside interactions, and continue this process over multiple rebirths which would eventually lead to Nirvana. Monkey King does throughout the book desire the need for immortality, but doesn't try to achieve it in the patient, care stricken way that a Buddhist would.
Throughout his journey, Monkey King is very impatient, and desires the need for everything right away, easy and quick. This is easily represented in his experience with the Dragon King. Monkey realizes that since he is now a ruler, he will need some sort of weapon to protect himself, and not always be forced to use a stick. So he visits the Dragon King in hope of finding one. During this process, Monkey is presented with multiple heavenly weapons, but he always seems to have an excuse for them. Finally he sees the pillar that keeps the island from floating away. Totally disregarding this point, Monkey besides to shrink the pillar and use that as his magical weapon. Even after all the Dragon King's begging, Monkey was set on taking the pillar without giving any thought to anyone or anything around it.
Another great example of Monkey's foolhardiness is when he becomes in charge of the Jade Emperor's Heavenly Peach Garden. Monkey is stricken with the fact that there are thousands of his favorite fruit that he has to take care of by himself, and some of them will make him immortal faster than studying or asking. So, his constant desire once again overtakes him, and Monkey starts eating f the peaches in the garden and can't control himself after that. Both these situations show how Monkey King's desire really take over his decisions over right and wrong. To Monkey King, his decisions are made over want and work. Overall, the Buddha would not grade Monkey favorably. I thought he deserves a D, similar to what I presume Confucius would have given him.
Also, the fact that he decided to mark his territory on the Buddha's fingers doesn't seem very favorable regarding mostly anyone's opinion...