Try Ana y Jose on the beach road going south. They have a small parking lot right off the road (on the left, water side). Nice service staff. The food is good and at reasonable (period, not just for Tulum beach road) prices. Drinks are good. There is a big open air, covered restaurant. Walk toward the water further and you can rent a bed, or sit (free with food/drink purchase) at a covered table in a kiosk right on the beach. There are bathrooms and showers. The beach there is nice, with rolling waves and not too steep. You can walk, wandering, from there down the beach in both directions..