matthewmaria

they have a list of what not to bring, cell phones are included on that list.
https://travel.state.gov/content/dam/visas/Supplemental/CDJ%20-%20Ciudad%20Juarez.pdf

i did this actually back in 2007 and was amazed at the seemingly high stack of paperwork that was needed to get married. if it was me, i would have your fiance check with sre to ensure you have everything you need. i remember the physical, the aids test, my birth certificate, the application at the registro civil and the letter. once approved from sre (i think) you only have 30 days to get married or you have to do it all over.
a little old but still pretty reliable, here's a link which provides a good place to start. I do remember i had to schedule the wedding. (something to keep in mind).
http://www.visitmexico.com/en/weddings/legal-requirements-to-get-married-in-mexico

I paid the fees online and then sent ALL the paperwork in one packet. Done this twice now (stepdaughters) first time worked great, so far so good on the second one. Received my letter in January, just waiting for the 60 days to go by before i start calling.