Spring break (end of March and beginning of April) and summer (July and August) which is the high season and the prime of all it’s touristic services, however, it is recommended to visit during the month of September and October because it’s temperatures are not that intense and you can enjoy the sight of a lot of animals. 

If you don’t travel in season or holiday, you may have a little more difficulty finding hotels or activities. But as an added benefit you will find the place to be much more.