I knew before I went to Mexico that smart phones would work there, but there wasn't much information on specifics. So, here's my story.
First, you're not going to get much help from sales people. They make money by selling phones and recharges.
Yes, your phone will work if you swap the SIM chip, but you have to unlock the phone before you do this. This isn't as big a deal as it sounds. I went to http://www.foneszone.co.uk/ and paid them ten euros. The unlocking code arrived a couple of days later, with some easy-to-follow instructions on how to do the unlocking. This worked with no problems.
The next step was buying a SIM chip, from Movistar. A lot of internet cafes sell SIM chips, and I went to one of them because the people who work there are more tech-savvy than the sales people you find in stores like Coppel and Elektra. The chip cost 120 pesos, and the phone connected to Movistar, and gave me a phone number, as soon as the chip was plugged in. Of course, this is useless unless the phone has time on it, so a bought 60 pesos worth of time. A day or two later, I set up an account on Movistar's web site, and used a credit card to purchase more time. When I did this, Movistar gave me some free minutes, and ½ GB of free data transfer.
I learned later on that you can mail-order Telcel, Iusacell, and Movistar SIM chips from www.mexicosimcard.com.
It turned out that getting data going was the biggest technical challenge. If you buy your phone directly from the cell company, it's already set up for you. If you got your phone somewhere else, you're on your own.
So, here's what works for an LG-P505CH running version 2.2.2 of Android. Go into “Settings”, and click “Wireless & networks”. Scroll up, and the last choice at the bottom is “Mobile networks”. Select this. Turn on “Data enabled” and “Data roaming”. Then select “Access Point Names”.
This is the hard part: you have to create an Access Point Name (APN) for your provider. Click “New APN” at the bottom.
Here's the settings that work for Movistar. The “Name” can be anything; just make it “movistar”. The APN is “internet.movistar.mx”. The Username and Password are both “movistar”. That's it. Click “Save”.
Here are the settings for telcel: APN: "internet.itelcel.com". The Username is "webgprs", and the Password is "webgprs2002".
Here are the settings for Iusacell: APN: "web.iusacellgsm.mx". The Username and Password are both "iusacellgsm". My experience with iusacell was, avoid it like the plague.
You then have to click the APN you just created so that the radio button next to it is yellow, so that this is the APN the phone is using.
Click the “back” button, so that you're on the “Mobile networks settings” screen again. Click the bottom choice, “Network operators”.This will give you two more choices, “Search networks” and “Select automatically”. Click “Select automatically”, and you should be up and running.
If this is working, you'll see small up and down arrows below the “3G” or "H" indicator at the top of the phone screen. (You may need to turn the phone off, and turn it back on again.) However, you will not see this if you are in your local coffee bar or some other place where you have a WiFi connection active. So if you want to make sure it's working, deactivate WiFi.
Now, how does this work in actual practice? I've successfully used Google Maps to get to where I'm going. I have K-9 Mail installed, and I can use it to read and send email. However, both of these operations drain the battery very quickly. You should disable synching in K-9. This isn't a real problem; all you have to do is tell it to “check mail” when you feel like reading your email. Even so, when you're composing email, it drains the battery quite a bit.
However, I've had no success at all using Skype or CSipSimple for making an receiving phone calls. This works OK if you have a WiFi connection, but if you don't, Movistar's bandwidth isn't high enough to support this. I would be interested in hearing what sort of results users of Telcel and Nextel have with this.
Movistar is a low-cost service, and you get what you pay for. On a recent trip from Guanajuato to San Miguel de Allende, my coverage stopped as soon as I left Guanajuato, and didn't resume until I reached San Miguel. So, don't expect to use Google Maps if you're hiking in the mountains. On the other hand, on a trip from Guanajuato to Guadalajara, I had coverage the entire way.
Article updated October 16, 2014