The timeshares that offer all inclusive are not worth it. You are better off to book through the resort or other 3rd party. October is slowest/rainest month of the year. The area is overbuilt at the moment.
This would be a great deal but too late for you:
http://ofertasimple.com/ofertas/pan...onita-todo-incluido-septiembre-ferias-patrias
The beach is not swimmable and when the tide goes out its rocks and dark sand.
Wyndham Corona is an all inclusive on the beach and goes for 8000 wyndham points. It is a hotel and not a resort so unless you really like the beach and small pool and drinking you would still want to use your car to tour around a bit.
As for car rentals there is a $30 or so mandatory insurance fee and possibly more taxes.
If you have a car and like to move around I would suggest staying in two places. There is lots to see. Be careful driving at night it is like grand theft auto out there.
Send me a pm if you need anything more.