As a Mexican / American familiar with travel there. I encourage you not to take your Storm.
Cheap GSM / quad band phone does wonders and you can either go the calling card route or pay for in country cellular services. Either way they are cheap, and you can talk nightly for very reasonable rates.
If you don't need portability and just want to make landlines, get yourself some calling card action at the local stores and use your room phone.
I am always too drunk to worry about cellular calls while out and about.