I am a single traveler and pre-COVID it was cost prohibitive to stay at an AI because of the single penalty being almost double the cost. Plus, the AI resorts are usually quite a ways from the downtown area and I like to explore local cuisine. Times have changed. Since the food choices are temporarily (or permanently) curtailed downtown, an AI seems to be a good alternative. To my pleasant surprise, the AI option is doable now during COVID for a single traveler, so I'm taking advantage of that. I have booked at Sunscape November 8-15 with a deluxe double ocean view room with the AI, excluding breakfast, for $930 USD, 7 nights, including the 19% tax, not including diving. I don't eat a big meal before the a.m. dive, so the breakfast exclusion is fine for me. I bring instant oatmeal for morning diving. Although I'm not a fan of third-party booking engines, I booked through Agoda.com because their pricing was so much lower than a direct booking, and I can cancel up to 1 day before arrival and no deposit required...again, COVID times.
The onsite dive op is Dive House, so I will book independently with them ($95, 2-tanks) and not through the resort ($116, 2-tanks), and I can dive as much or as little as I want. Nitrox is $12 per tank, a ripoff because I don't think we should pay extra for Nitrox in the first place. I love night diving and hopefully the restrictions will loosen by then. They do night dives Monday, Wednesday, and Friday.
To the OP, since you're a first-timer to Mexico, here's a few travel tips.
(1) Don't be lured into free stuff with a time share presentation. It's like being married...you'll have a noose around your neck for the rest of your life.
(2) A polite "No, gracias," is your favorite response to the street vendors/hecklers if you're not interested.
(3) The taxi mafia (as I call it) or the taxi union have set rates by zone, but the taxi drivers WILL try to overcharge you. It happens to me at least 50% of the time, but I know my zone prices before I go, and once you challenge them on it, they accept it. I call it the taxi mafia because transportation is run by the government and that's why hotels aren't allowed to offer shuttle services and there's no Uber or Lyft in Mexico. The dive shops aren't allowed to offer transport on land, only by sea. Also, stay away from the taxi stands because you pay extra for that. Walk a few feet down the street, put your arm out to flag a taxi like you're in New York, and a taxi will pull over right away and whisk you away. Tipping is not customary for taxi drivers and pay in Pesos, not USD, because you definitely overpay in USD.
(5) Most everything in town is closed on Sunday (at least Pre-COVID). Sunday was the only day cruise ships were not in Cozumel, so that was the day off for most of the island workers. Diving, though, still runs on Sunday. The cruise ships used to bring 10,000+ people to the island every day, six days a week.