Some phones get reception in Tijuana without roaming charges and others do with roaming charges.
I have--and like--T-Mobile. It has a roaming fee when used on the streets but no roaming fee with a Wi-Fi connection.
The AT&T Go phone works in TJ. It's a popular through away phone.
AT&T plus Cricket (which uses AT&T towers) have coverage in lots of the downtown and ZN areas of Tijuana.
T-Mobile charges $15.00 a month for 1000 minutes of calls to Mexican cell phones. (Always be sure what you are buying allows you to call Mexican mobile phones. Not just landlines, which nobody has.
KeepCalling dot com and Google Voice are phone apps that allow an American cell phone to call Mexican landline and cell phones for about five cents per minute--as low a rate as it gets. Minutes bought for either app never expire, making them better for light usage than something like T-Mobiles $15.00 a month fee.
I the Google Voice app. It has several settings, one of which makes it to be a "set and forget" app for making International calls.
An example of what to dial when using a US cell phone to call a Mexican mobile phone is: 011-52-1-664-987-6543. Where:
011 is International access (you can use the + symbol instead of 011)
52 is the country code for Mexico
1 is mobile phone access in Mexico (which is omitted when dialing a landline)
664 is the Tijuana area code
987-6543 (which a Mexican is more likely to write as 987-54-43 or something like 66-49-87-65-43) is the local phone number
