According to a few sources- When renting a car in Mexico you may want to keep a couple of things in mind. There are a lot of car rental companies within Mexico and the Riviera Maya which can be divided into international, regional and local operators. No names will be used here, just use your preferred internet search engine and type rental car Playa del Carmen or something similar.
International companies are providers and can be found on any airport in any country, especially the well known ones. The advantage is they have lots of cars with quite a choice, if you have a problem they come get you and get you a new car but they can be a bit expensive, however, they have cars at the airport, you fly in, get your car, do your beautiful cave diving thing- or just general sight seeing and drive back to the airport when done.
Regional companies are small rental car operators who have a office or station outside the airport but provide pickup from the terminal to the off site car location and another office or station in Playa del Carmen. If you have trouble with your car you don’t have to get back all the way to the Cancun airport but can change the car in Playa. They will however not come into the middle of nowhere and get you a new one. They can be cheaper than the big ones as they have less overhead. Car choice might be limited. You still pick your car up at the Cancun airport and drop it there when done with your trip.
Local operators area a one stop location with only one office or station in Playa del Carmen that can have the best deals as they are small with no overhead. You have to get to Playa somehow either by bus or airport transfer and then get the car locally. They will not come into the bush to bail you out and car choice might be limited. Once you are done with your thing you need to drop it in Playa and get somehow back to the airport via bus or transfer.