car or no car??
 

We will be leaving on the 20th, Playa del Carmen , first time..staying at Mayan Palace. 2Adults.
Should we rent a car?
can you walk along the beachand swim a sit even if other hotels are there?

Car rental pretty risky and not needed.

Mostly no problem walking the beach...

In the past, we've rented a car for a day or 2 - it's nice to be able to explore the area a bit.

If you decide to rent a car it can be fun to be able to go where you want and when you want. Since you're at the Mayan Palace you'll be 20 minutes out of town. You could take a taxi from the resort or you could take the hotel shuttle out to the highway and then wait for the colectivo to take you to Playa or points north or south if you wanted to do that also.
On the not so great side of renting a car...
take the extra insurance and it will cost you more than the car rental will. There's been lots of discussion about this pro and con. I have rented quite a bit but no longer do so. It's just too much of a headache between the gas station attendants trying to scam you and the possibility of accidents, dents, etc. or being pulled over and ticketed.
The rules of the road are also a bit different in Mexico although with the highway widening it's been pretty nice driving. There is a lot of road construction in PDC as they are building flyovers for the highway so traffic has been backed up more than usual.
Do your homework and decide what you can live with. If it's important to be able to get out and around, then rent but be sure you know the differences of renting in Mexico.

It depends what you want to do. If you want to sit on the beach and drink at the hotel bar, why bother? If you want to see the Mayan ruins or cenotes, then you might want to consider renting a car.

We wouldn't have done this trip without one, but we've spent a lot more time at ruins than beaches.

If you rent with the local rental places, they include the insurance, but the car is still about $40/day for the lowest end car.

The gas station thing seems overblown to us, but we took the advice to only buy 100 or 200 pesos of gas, and haven't had any problems at all. We're in Tulum, and got gas in Valladolid, not PDC though.