Driving along this coast isn't difficult. There's only one highway, so you can't get lost. Speed limits are clearly posted, but lots of cars ignore them, except around Playa, where police are known to ticket drivers. Watch your speed when you're passing through town. Maximum speed for the center lanes is 60kmph (40 mph) and, for the outside lanes, it's 40kmph (25 mph).
South of Playa, the highway is four lanes as far as Akumal. South of there it's still undivided. You're not allowed to stop on the highway to make a left turn. You're supposed to pull over to the right and wait for traffic in both directions to clear before crossing the road. Another tip: Drivers here customarily pretend that there's a center passing lane. Oncoming traffic moves to the right to make room for the passing vehicle. You should do the same, but look out for cyclists and cars on the shoulder. This is why I recommend not driving at night. There are several more gas stations in the Riviera Maya now, so you shouldn't have a problem getting gas. But make sure the attendant gives you back the right amount of money -- I've had people try to short-change me.
