We highly recommend Uber. We strongly advise against renting a car, it is complicated and not needed. Both hotels offer airport transfers.
There will be shuttles from both hotels. There likely will be 2-3 return shuttles to the hotels. If you need to leave at different time, you are able to take an Uber from the venue.
You shouldn't need to bring cash in advance. You can take out pesos at an ATM if needed.