I've never seen a dive operator that allowed a diver to dive without a buddy or to dive 20 or 30 feet above the other divers. I've dove Cozumel 5 times and the operators I've used don't require computers, but strongly suggest them. Personally, I don't ever want to dive without one. Now, as far as buddies go, some are great, some are good, some are OK and a few are awful. I travel alone, so I am at the mercy of who I get assigned to. But I always stay close and check in. I prefer it when I get to have the same one and hopefully get a good one. And I pretty much glue myself to the group.
You might want to try another operator. I've never been assigned a buddy in CZM when I wasn't diving with a friend. I've gone up to the surface several times by myself and well out of eyesight of the DM.