Been to Cancun, too. It was pretty, but I prefer Puerto Vallarta; vacationed there twice.
Went to Acapulco when I was 17 after I graduated High School. 1977, then I joined the Army. (US, NOT Mexico, LOL!)
Went with my BFF at the time and we had an absolute blast for two weeks. Don’t tell my Mom, LOL!
We spent most of the time inland, climbed some pyramids and saw many great jungle birds. There were a couple of lagoons south of Cancun where we spent a couple of days snorkeling. It was amazing.