Actual good advice. During a business trip in India got taken to Agra to see the Taj Mahal, the grounds of which are peopled by thousands of monkeys. We were told not to even look them in the eye as they would respond aggressively. One could run up and bite chunks off your face before you'd know what was happening. Nasty little buggers. They are only limited to throwing feces at visitors in the zoo because of the cage.
I worked with various types of primates as a zookeeper.
Some of the macaques were aggressive. But other monkeys were quite friendly.
There was one large male chimpanzee that no one trusted. We once had to enter his area, and we had two men with 30-30s aimed at the tranquilized chimp in case he woke up.