I don't know about international texting, but you can get an unlimited text package that covers all lines on a family plan. That package also includes free mobile to any mobile (not just another ATT mobile) That can really cut the minutes used. I think you have to have at least a $69.00 @ month plan to add that. (700 minutes) They usually will waive the upgrade fee on the primary line for accounts they want to keep. I have successfully called in later to have another removed. There are plans that include Canada and also Viva Mexico. Some cover texts to: but not from within those countries.
They are not going to give you a deal on a loyalty basis for such a small user.