The apertures and or burners would be different, just like a home stove converting from natural gas to propane or vice versa. On the home stove most people would just buy a new one. I'd check with the manufacturer to see if propane burners can be fitted, if so it should work just fine. I'm assuming the CNG stove has the same safety shut offs as a propane one and you have the solenoid valve, proper tank locker, etc that propane systems require. The tanks are different too so you'll have to replace that as well. If you have all that stuff already, changing the burners would be the way to go if you can. If not, then you're in for a huge expense to convert.
Non pressure alcohol is another option. No additional safety equipment required and the fuel is available anywhere. Last time I was in Mexico (many years ago) I saw 100% ethanol for sale in a liquor store. They drink the stuff down there. Alcohol only burns about half as hot as propane so it's not very efficient, but most folks who have the non pressure stoves seem to like them. Stay away from pressurized stoves though, they're very difficult to light and cause a lot of fires.
CNG doesn't require the same storage requirements as propane. They can be placed anywhere on board since CNG is lighter than air as opposed to propane that is heavier than air.
I know that CNG can be hard to find, especially once you leave the US. Since a lot of modifications need to be done, both to the stove and tank storage requirements, I think I'd get an extra tank or two for the trip and stick with the CNG.
I did the conversion from CNG to propane. All I did to the stove was change the size of the orifice by soldering the hole closed then redrilling it.1 cubic foot of propane contains 2,516 BTU and 1 cubic foot of natural gas contains 1,030 BTU, so the area of the hole for propane is about half that for CNG. If you google "convert stove from cng to propane"
you will find a heap of info. And I have the propane detectors and shut off solenoid and the tank is outside on the stern.
Stove works just fine. Others have done the conversion and as others have posted some manufactures have a conversion kit.
I remember back in the 70's people converting their propane appliances to natural gas (same thing as CNG) by changing or drilling out the orifices. Real easy. We're just making the change in the other direction. I don't know if the OP's stove has the safeties or not, I imagine some do. Also the solenoid, sniffer, and other equipment. None of that stuff is actually required by law, it's just a darned good idea and AYBC code, which is really just a guide line. Some people get away with using camping stoves for years, others blow up the first day.
The installation doesn't really have to be that expensive. I built my system using a Fireboy solenoid / alarm system (about $300 at the time), brass gas fittings from the hardware store, hoses from a local industrial hose shop, and two 20# patio grill tanks that I already had. The tanks are steel, but I'm in fresh water so the corrosion isn't much worse than it would be on the patio. I can also swap them out at a gas station of I can't get to a propane fill station. I built a plywood locker to enclose it all and hung it on the rail. Everything is code and I don't think I have $500 in it not counting the stove.
If you paid West Marine prices for everything it would probably be twice that or more.