I cannot speak to Solo Diving in Cozumel. However in early June i scheduled a Thursday AM Spiegel Grove dive in the Keys with Horizon Divers. I couldn't find anyone to go with me so I showed up and signed in. They asked at the desk if I had a buddy and I said i was diving solo. They gave me a 2nd release form that was an additional 2 pages. I had to copy a full paragraph of text in my writing to the 2nd release basically saying i was going to kill myself. Next question was if i needed to rent a pony bottle. I happen to be on doubles so i was good. They teach the solo course so they allow it. Based on my experience I would check for shops that teach the SDI solo or Padi self-reliant course and see what suggest for the solo dives.