I'm VERY jealous. My wife and I have contemplated moving to Merida as well. I'm a screen printer, I would love to set up a small operation there someday.
I don't know any screen printers there, but there is a screen print supply house right on Paseo de Montejo. I can't remember the cross street, but it's about .5 mile south of WalMart. They might be able to point you to a good printer in town.
So what is prompting you to move to Merida?