I can’t give you a definitive guess based on your description, I knew you were writing from southeast Florida as soon as you described this large, strange lizard. There have been more exotic reptiles that have become established in your area than even the field guides can keep up with. Currently there are Knight Anoles, Spiny Iguanas, Giant Ameivas, and Basilisk lizards living and breeding in your area, ( these are all within the size range you describe), and none of them are native to Florida. Who knows, the “colony” you describe ma be the next new invasive species that hasn’t even hit the charts yet. See if you can get a decent photograph of one of these mystery beasts and send it to us, I’d love to see if I can figure out what it is.