Not to be argumentative, but this is somewhat misinformation and something that gets pushed around alot that annoys alot of the mexican cave instructors. Sure there are sm passages in alot of the caves, but you can dive pretty much any of the systems from tulum to PA in backmount easily. Once you get down to the Muyil area where catepillar and whatnot are, its definitely more sidemounty. I remeber 12 or 13 years ago on my first trip to mexico I thought I would be best in sm since that's what gets said so often. Totally inaccurate. You can spend years diving that area in backmount without ever having or feeling the need for sm. I have almost as many cave dives in mexico as I do florida, and there's only been a few times where if I were in bm I would have to call the dive. But those are also caves well known to be sidemounty in spots and we were exploring those spots (in sm).
There's just alot of blanket statements made about mexico without context which is the issue.
I remember my first trip I thought I had to be in sidemount, thought I'd be the only f'ing weirdo in a drysuit(like I've experienced in Bonaire and got looked at like I'm the elephant man), and that all of the police and gas pumpers are scumbags that want to rip you off at any turn. There's only one truth in that statement that holds up and it's that quite a few (not all) of the gas dudes are just looking to rip you off.