GSM Phone ?

When talking with Sprint support the other day, the subject of their horrible rates calling/receiving from Mexico came up. The person I was talking to indicated that since our new Samsung Galaxy S3's were "GSM phones" and not locked - we could purchase SIM cards from Telcel or whomever and use them in our phones while down there. Something tells me that this is inaccurate info based upon all the posts I have read about having to get NOB phones unlocked. Any comments from the experienced ones?

My other thought is to just take my old LG Lotus which has worked previously and apparently can accept 2G & 3G networks and turn it into our Mexico phone for our short trips.

Usually if you buy a phone "outright" it is not locked to a specific carriers network however if you get a "free" phone along with a monthly plan it is indeed locked to that carriers network and would need to be "unlocked" to use on a different network. If you have met your contractual obligations with your current carrier (IE paid the phone off) you can get them to "release/unlock" it for you.

do a google search for "imei" and your cell model.
many sites to input this number, and get info as to if its locked or not.
the number should be on a tag, under your battery
there are some codes you input, on the dialer, to retrieve this info as well

If you buy your phone north of the border with a data contract it may be locked.  If the smartphone is compatible with the US AT&T smartphones then it should be compatible with the Mexican GSM network. I bought my Samsung Galaxy S3 in Guadalajara and it was unlocked without a data plan.  So all I had to do was just buy a SIM card and put it in after I got the SIM card size trimmed to fit in my Samsung Galaxy S3 which uses the new micro SIM.  Ahmed in the phone store that is on the Ajijic Plaza can easily make the adjustment.

I was given this information prior to purchasing the S3 with a Sprint voice and data contract. As it so happens, I have to make a stop at the Sprint store this afternoon and I am going to ask to find out for sure. We have no intention of using our phones for data and will turn data off when in Mexico. It galls me that Sprint doesn't even offer a Mexico plan and $2.29/minute is way over the top. It isn't like we plan to use our phones a great deal however any NOB calls we make will be made through WIFI connections.

I also plan to take our old phones (LG & Sanyo) into Sprint to see about getting them unlocked since the contracts were completed a long time ago.

My visit to the Sprint store resulted in a conversation with a clueless tech who provided me with enough inaccurate info to not believe a word out of his mouth. He did a song and dance on whether to S3 was locked or unlocked and if it could be used with a Telcel SIM Card. He outright lied to me when he stated at both the LG and Sanyo phones could not be flashed to use in Mexico. I have found YouTube instructions for doing so or there are services which one can pay to have it done.