Good basics on that above link, if not a little too self-promotional.
That said, I have no personal gain from reminiscing over the services I once enjoyed...
So my 2cents - having gone with zero Spanish, and then lived there 3 years -
Other than the hassle of registration mentioned on link cited above, enacted during my stay, which I would think can be planned ahead for, including buying at a border/major transit location where they're glad to sell to you and will know the details...
I would recommend buying 2 cheap cell phones even for your short stay. My reasons, in no particular order, being: Cheap, Reliable, Safe.
I had the benefit that my partner is from Mexico, and knew what to advise. But I had to go on my own to shop for the phone & all, and his advice turned out to be right.
I used Movistar the whole time, with the same phone
so I can speak to it being the best deal (in '07-'10).
I lived in a major metro area 2 hours outside of Mexico City and traveled around a good bit, through remote areas and towns too. I worked alot while there, so contact with clients was important.
(Info links in Spanish for Prepaid "Pay by the Second" »www.movistar.com.mx/Telefonia-mo ··· repago-Q
I got mine for =USD$20 -a Nokia 1112, was nearly the lowest-end phone of their offering in late '07-'09.
I looked at their current deals, all seems the same for the basics, including phones at that kind of price-point. They differ on battery life, but the Alcatel for $249 pesos has 5hrs while other have 2.
The best part is that you get free unlimited minutes/SMS to 2 numbers you select
by opting in. (i.e.code*343) »www.movistar.com.mx/Telefonia-mo ··· egundo-Q
So the two of you can have all your minutes/SMS FREE. One of the 2 does not have to be a Movistar number.
Their site looks complex at first, but all works out once you get the gist of it.
Another tip, when you buy time in higher increments, the bonus time is disproportionately augmented as well, so it pays to start out with $200 pesos, since your stay is short, if you wanted that backup to be there.
These promotions gave it extra value, like this one:
If you buy the phone and activate right there they add on double the minutes for the cost. Movistar Promo
Promo follow through was 100%+.
So ~USD$20 ($200 pesos) would get you 55 minutes + bonus time added.
• Perfect signal. Even inside concrete buildings which is most of the structures I was in all day and night. Never missed/lost a call or message. Even while traveling, reasonably populated towns and semi-urban areas had signal. I came back to the USA totally unprepared for the service/signal failures I've now endured for 2 years. I was so NOT aware such issues could even exist, having had the old T-Mobile before that.
• No expensive equip to worry about getting stolen/targeted over. This was a very real risk for us, and for any woman alone for any real length of time- the less flashy the better. The only phones we ever witnessed being stolen, were mid-end to lower high-end ones, belonging to our Mexican friends. Of course, higher/lower risk depending on the area you'll be in. I was glad I could e casual about using mine, though I thought the admonition had been a bit paranoid in the beginning. It turned out to be true, so added to my comfort level while busing and shopping, in the many places I set it down on a table or it could have been snatched away effortlessly.
• No worries about your USA device settings, setup, accidental changes, or anything. And as for a cheapie phone- these low-end models have faded in our memories here, but they're still easy to use.
After my disappointment with USA service upon my return, I really wouldn't want to deal with any USA-based billing hassles or nonsense, but then again I just recently bailed out of T-Mobile and ported to Google Voice, but I digress.
So it looks like for USD$80-90 tops, you could have unlimited service for you both
for your stated purposes. Presumably in one transaction and take 'em home. Refills are easy if you need 'em, and I never had any problem at any little shop that sells that company's refills. They all work fine. You get your confirmation while you're standing there. Less worry than messing with online transactions I think.
Re other cell vendors: I know Telcel & Nextel were more prestigious and $$$. Alcatel seemed the choice for exec levels who wanted consistent remote area service.
Hope some of this helps. Have a good time!