There are small bars at fisherman's beach, although I would not go there with a purse .. just carry your $$ in your pocket. It has a little fresh water cold stream running through it and you can cut through to Margueritiville as well. Be prepared to buy some trinket there though as respect, tip well and try some of the local cooked food and you will fare well there. Just be firm with others approaching you, and when you get seated just tell the rest that might come up to you, that this is where you were going and that you prefer some peaceful time there.
Also, although you will need an escort, there is a waterfall if you can climb down and up the hill, just up the road from the cruise docking, past the helicopter pad. The guy there has a small shack where you can buy beer. You need an escort for this though. I'm sure one of the red plate cab drivers would take you there.
Good luch and enjoy.