If I were a Mayan facing ecological disaster
The question in my mind is this was a technical, engineering wise, society living on a land similar to Florida, that eventually disappeared. So where did they go?
If it were me, I would make my decision based on moving to real estate that would make it militarily impossible for my neighbors to conquer me. The land would have to be surrounded by mountains too high for convenient armies to cross. It would have to be a land with a ready fresh water supply and renewable fertile soil for agriculture. I would be looking for a land with valleys surrounded by mountains. Something similar to Switzerland would work.
I would be looking for solid rock. I would look to go underground. Possibly into water caves, I would build my houses and temples in a manner to anticipate dramatic geological disasters. That means that there would be a surface civilization for conquerors to raid and pillage. But the real civilization would be built into old extinct volcanoes, mountains with very old rock, and the visible entrances would be hidden well against discovery. Northern California, the Rockies, Central America, Peru, Argentina, and even possibly Antarctica in warmer times all suggest themselves. Islands in the mid Atlantic or even areas of the South Pacific are possible. The more remote from civilizations the better.
I suggest an underground civilization partly because of their engineering skills. The idea being to make the Mayan civilization disappear from the outside world. If they believed at the end of the age the world would encounter a massive destructive event, they might have prepared for it by having their own version of fallout shelters.
The best structure would be one made of stone. It would be built in the form of pyramids. I suggest that they built such pyramids underground. The motive was the massive barbaric peoples surrounding the area. It was impossible to survive these war people. So they did the next best thing. I suggest they built their homes up to 400 feet buried into the sides of mountains.
If it was me, I would have made impassible amazon jungles as part of the defense. But the ultimate defense is still solid rocky mountains with limited access. Even with millions of warriors, if you can only pass one or two people through the caverns at a time, it is impossible to conquer a people buried in rock. At least with primitive technological skills. The other thought is if it is invisible, the warriors do not know it is there.
I would set up gas defenses. As warriors got uncomfortably close, I would eliminate an entire army of them camped in a valley by killing them as they slept. Since the underground caves would be air-proof, the vents would be high in the mountains and air pumped in. Rock doors would seal the caves while this was going on.
The leaders of such a civilization would anticipate treachery from within. This would mean a priesthood devoted to keeping the people safe. I suggest the entire civilization would religiously keep their existence hidden. Thus when the Spanish people invaded they would be the only ones prepared. The Spanish could go throughout the entire land mass and never see them.
Quietly, the Mayans would let them take over the surface. Meanwhile, they would continue to exist in a civilization buried deep underground without much fear of discovery from the surface dwellers.
All that would be left on the surface would be the abandoned structures of an earlier age.
The other advantage of an underground civilization, possibly 400 feet below the surface would be retarded aging. The surface radiation of our planet ages us prematurely. The atmosphere no longer protects us completely. Such a civilization might live an average of 100-150 years of age. Especially if they added diet to their science in such a way that people slowed the aging process. The very rock around them would shield them better than we are shielded on the surface. Next time you check your body out. The cloth-covered areas do not wrinkle like the areas exposed to the air and the radiation from the Sun.
The other advantage is temperature control. At the surface the temperature of the soil is 52 degrees fahrenheit. Deeper it gets hotter. So at some point you would be at a comfortable 68 to 75 degrees. This is year-round temperatures. The main problem of course is food production. An engineering solution is biospheres under the ground where light is guided to farms. The more likely solution is surface produced crops in the mountain valleys stored in ice caves high in the mountains.
Well, so much for my imagination today. But that is how I would have solved the Mayan problem with hostile neighbors.