If you have "never been there" let me be the first of many to tell you that "rent a car" is not the wisest thing to do. At least not at first.
Transportation is provided, door to door, for most of the things you will be doing.
I hope you can go to Damajagua Falls, if you are in good physical shape. Snorkeling is fun. So is catamaran riding, four wheeling and "jungle buggying".
A lot of things will be suggested, so you can pick and choose.
One thing that will not be suggested is for you , a newbie in this, our paradise, to rent a car and drive our far from paradise roads!!
There are great cars and drivers available, English speaking, that can run you all over the place at a cost that is equal to or less than renting a car. Please, leave the driving to 'them.' One is called Wilson and he is well recommended.
HB