Probably. Otherwise known as international. Not 232bar 5 thread DIN and not 300 bar 7 thread DIN. Nor the M26 nitrox style nobody ever buys.
I am wondering if (say) six of us up with DIN regs if that will be an issue for a typical operator, aside from the people with the steel tanks.
We could find adapters but they are ungainly and defeat the object of using DIN.
Yes, A-clamp is the same as yoke.
Yes, DIN regs will be an issue for a typical operator. Most dive ops in Cozumel use 80cf aluminum tanks with yoke valves. These valves are dedicated for yoke fittings, they are not the DIN valves with screw-in yoke adapters you refer to, so your DIN regulators will require adapters which run around $40. Here's an example:
XS Scuba Din To Yoke Regulator Adapter AC370 with reviews at scuba.com
Yes, the adapters defeat the object of using DIN, but the fact is that the vast majority of dive ops in the Caribbean and plenty of dive ops outside the Caribbean use yoke valves exclusively. You are actually fortunate that there are exceptions to this general rule on Cozumel.
You could assume better gas consumption in warmer water, but you might be mistaken. Some divers prefer the comfort of limited visibility and may have agoraphobic issues when they can actually see how deep the wall goes, for instance. Drift diving usually leads to less air consumption, but some divers inexperienced with drift diving may fight the currents or be uncomfortable in them and thereby end up using more air than usual.
The shops that use larger steel tanks also allow for longer dives, with 70-90 minutes being closer to the norm instead of the exception, so it's my feeling that one gets one's money's worth with the extended bottom time.