The good news is that the school always pays on time and the curriculum, though not stellar, is at least adequate to cover the class period. San Luis Potosi is a lovely town, the students are friendly, the food is good, and the weather great. The school has lived up to it's promise of Spanish language training.
The bad news is that you're completely on your own in teaching, except for the mediocre textbook--there's no direction or training. You'll get almost no assistance from the owner, but you won't be bothered by him either. He's not a people person and will say just about anything to get you to leave his office. Don't bother to make appointments with him. He probably won't show up.
I was promised a one year contract, but there isn't one. I was promised pay for school holidays, but didn't get it. There's no guarantee of hours and you will only know your schedule 4 weeks at a time--and you won't get that schedule until the last possible minute, take it for leave it. You pay your own airfare, housing and work visa, so the owner has zero investment in his foreign teachers. You aren't even picked up at the airport or given a tour of the city. Not even a map. He'll arrange for housing, but he won't have ever seen the place, won't take you there or know how much it costs. He will let you come even when he has too many teachers. It costs him nothing.
It's not the worst place I've worked, but it's the city/people/culture that makes it worthwhile to be here. I've seen a dwindling enrollment that makes me wonder about the long term financial stability of the school. BEFORE COMING, MAKE SURE TO SPEAK WITH A CURRENT TEACHER AND ASK ABOUT HOURS/PAY/CLASS SIZES. If you can't get a current contact, assume something is wrong.