You heard correctly, Kalie, to the extent that that there is not a very large expat community in Tuxtla if, by that, you mean large English speaking expat community consisting of expats from the NOB U.S. and Canadian communities. I would also say that there are also few expats of European origin. There are a significant number of expats from nearby Central America many of whom are employed in and around Tuxtla but few if any of them would be reading or participating in this English language fĂłrum.
While we spend our summers at Lake Chapala, we spend our winters and springs annually in San Cristóbal de Las Casas just about 45 kilometers up the escarpment on the autopista from Tuxtla and visit Tuxtla and Chiapa de Corzo often for shopping, necessary business with various governmental and non-governmental functionaries headquartered there in the state capital, luncheons in some of the city´s fun eateries, some sightseeing and passing through in transit to some other parts of Chiapas State - that sort of thing.
I doubt you will find many expats (or anyone else for that matter) in the greater Tuxtla área who speak more that rudimentary English if that. Personally, I like Tuxtla and (even more) Chiapa de Corzo despite their stifflingly hot and humid climates at about 1,300 feet and enjoy driving down from often damp and chilly San Cristóbal at about 7,000 feet. After you become settled in Tuxtla and, if you are like most newcomers, decide to drive up to San Cristóbal for a serious change of pace, let me know by PM and I´ll join you for coffee at San Cristóbal´s delightful principal plaza for that cup of coffee.