Iphone 4s to iphone 5s

Okay so around august 2012 i got an iphone 4s that was handed down to me by my mom who had it for about 4 months and she switched to iphone 5. Now i want the iphone 5s for christmas and my grandmother wants an iphone so she asked me if i'm planning on getting a new phone. I told her yes and i want to know if it will be unlocked once my 2 year At&t contract is over. She doesn't live in US, Florida. She's visits every year for about 3 months mostly up to 6 months a year.
If the answer is yes for it being unlocked after contract can she use it on At&t month- to- month payment in Florida? She lives in South America, Peru and her 20+^ son has an iphone 4s so she can get guided. Iphone in Peru is around $600-$800. Less with contract but she travels alot.
Will my iphone be unlocked after my 2 year contract with At&t is over? What's the best opitions/ solutions i can do to get my self an iphone 5s? I think my parents and grandparents can spend together around $400.

First, contact att and ask them to unlock your phone when your contract expires

consider getting a sim card from a local carrier for use in peru.

You need to call AT&T and ask them if they can unlock it for you. Sometimes they won't unlock it for you until after the contract is up, but it's worth trying now.

If she is going to use it on AT&T prepaid/month-to-month, it doesn't need to be unlocked, she just needs to establish the month-to-month/prepaid service and get the SIM card for it. If she is going to use it on a local carrier in Peru, then it definitely does need to be unlocked and she'll need a local prepaid Peruvian SIM card.