Does the technology exist. . .

. . . to convert a gasoline powered vehicle to a different system?

Yes, you can easily convert it to propane or NG or for a much bigger price convert to electric assuming there is a kit available for your vehicle.

Thanks, Bob. Can I convert my car to propane here? Who would do that? And would my car then burn clean and produce no nasty emissions?

It will burn cleaner however you can expect about a 10% loss in power. Also I'm not sure how many propane filling stations there are here in Mexico. You could talk with the propane sellers or even one of the delivery drivers as many of their trucks have been converted to propane.

Excellent, thanks!
I assume one would need an expert mechanic to convert the engine over, right?

Better to convert diesel to a greasel and have free gas pretty much for life.