I think you should look at this link and that all the teachers here in Mexico were hired through TeacherMexConnect and this was not written by their company and this can be verified

http://www.sharynita.co.za/tag/teachermexconnect/

Some countries, like Japan, require you to have at least a degree in something, but Mexico is not that strict. A TEFL certificate will do.
Then, I signed up with TeacherMexConnect. Actually all the teachers at SEA got the job through this website.
The deal is you sign up for a lifetime membership for US$40. You then send through a one page CV and they send it out to their network of schools across Mexico. I think you can specify if you want to teach kids or adults, where and what level, but I wanted to keep all my options open.

Then you wait, and within a few days the emails from the different schools should start to come in. The schools will deal directly with you. TeacherMexConnect will keep your CV active until you tell them you are no longer look for jobs.
Of course, if you ever wanted to find another job, you just drop them a line and they will reactivate your CV and send it out to the schools again at no extra charge as far as I understand.
It was a really simple process and I had about 9 job offers come in in the space of about 2 weeks. SEA was actually the first to reply to me, but I wanted to see what other offers came in. Some schools include accommodation, benefits etc, so you just have to weigh it up and see what works out best for you. Generally the school will help organise and pay for your FM3 work visa once you get there.
Personally, for the pleasure of living in Cozumel, I have no regrets for choosing SEA! For the ease and results, I highly recommend TeacherMexConnect. They were efficient, friendly and reasonably priced. It was kinda fun too to put my fate in their hands and see what opportunities presented themselves. I am infinitely grateful for where I ended up!