Cozumel is open, the pier was destroyed, so you will be tendering in. Check with you cruise line to see which excursions are up and running. It might be a good idea to book thru the ship as the transportation infrastructure is not yet totally restored.
I called Carnival the other day to check on the February 9th sailing of Inspiration's stop in Cozumel. Keeping in mind this was a Carnival rep, I was told that they were limiting the number of ships that were going there, but all shore excursions were up and running and many shops were open, etc., and she also let me know about the tendering the other posters mentioned. I agree that booking any excursions through the ship is a good idea, provided your ship is not diverted to another port.