You are staying in cabanas on the beach! This place has a terrific website and makes staying on the beach look very romantic which is why we decided to stay there - and it is. You are in cabanas on cliffs overlooking the sea. Some are directly over the water and the breeze from the sea is cooling and refreshing.
It is incredibly beautiful. But if you go in the summer you should know that it is incredibly hot and buggy! You sleep under a mosquito net. These are tiny cabanas with no real security except for a padlock. It is hot inside! If you pick one of the cheaper cabanas, it will not be near the water and you will not feel the breeze. Unless you pay around 80-90 dollars for one of the cabanas up on the hill, there are no bathrooms inside the cabana and you share a cabana type bathroom with everyone. Get one of the more expensive ones!
Remember also that there is no electricity so pack accordingly with candles, flashlights, etc. Even though the website says you will see giant turtles at night, we never say any. Nearby Akumal has many turtle sightings so go there if that is what interests you. Having said all that, after we changed accommodations to one of the larger cabanas facing the sea, we really enjoyed our stay. The beauty of the water is incredible, birds soaring, waves crashing etc.
There is a nice inexpensive restaurant there with a nice atmosphere and good food. We are vegetarians and they always had 3 or 4 vegetarian dishes, mostly rices and spahetti. You are able to walk to the ruins of Tulum from Cabanas Copal. We did- but it was exhausting in the day's heat - take a taxi instead. Cabanas Copal is also in a good location to walk to several other hotels and restaurants nearby, as well as a little store.
We didn't sleep much in the heat there, but we did meet terrific people and the "natualeza" can't be beat! another tip: I had to go to a bank in the United States and pay in cash ahead of time for the accommodations. This might not be necessary now -- I think you could also pay using paypal.