Movistar Mexico in 2012 continues to be an excellent value when traveling in Mexico with an iPhone. You will need an older model jailbroken/unlocked iphone (3G, 3GS, 4) or an unlocked iPhone 4S including Verizon’s 4S iPhone. An unlocked Verizon 4S iphone comes with a Verizon SIM card which allows it to work in GSM countries. Most Verizon employees I have talked to are unclear about the iPhone 4S’s GSM capabilities. I think Verizon would prefer you use their included SIM cards internationally, but don’t, the international roaming rates are very expensive; when your Verizon iphone detects that you have arrived in Mexico, you will receive a text message from Verizon with their Mexico roaming rates: Global Data is $5.12/MB, texts are 50 cents each, and voice calls are $1 per minute. Your calls with a Movistar installed SIM are two cents a minute.
Getting a Movistar SIM card is a quick and fairly simple process but you must find a Movistar office that sells their SIM cards. All Movistar stores sell extra minutes but many of the smaller kiosks do not have SIM cards in stock. Movistar Mexico does not sell any GSM phones with the so-called micro SIM cards, though this probably will change, as most carriers are now selling the punch-out SIMs, which allows you to punch-out either the traditional or micro-sized SIM shape at purchase. This means you need to trim the traditional SIM down to the micro size. This takes some care, but not surgical skills. First time you attempt this procedure, under-trim the card initially, and if necessary, shave the card more until it just fits into its SIM slot.
A prepaid Movistar SIM card costs $12 or 170 pesos and your new account will also be credited 100 minutes. Have the Movistar sales agent activate your new SIM card with the agent’s personal phone in the store. If you need to check your Movistar balance dial *12536, you will receive a text message with your current balance. You can use cellular data with a prepaid account on Movistar’s EDGE network which is fine for email downloading, but limit your cellular data roaming. If you use WIFI for most of your heavier data needs, you can easily continue to use your iPhone in Mexico for a reasonable price.