I'm so jealous! I've always wanted to visit Peru. I know how important it is to keep in touch while traveling so I understand your concern.
Unfortunately, there isn't an option on the phone for text messaging auto reply. However, I know there are some 3rd party apps that will do exactly what you want. I am unable to recommend specific apps but you can visit the Apple store to see if you can find one for your phone.
If you really want to have access to your phone while in Peru you can always take advantage of our Global Travel Program. Visit http://vz.to/WeWBYP for complete details.
I trust this information has been helpful. Keep me posted if you need further assistance.
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It looks like Verizon just added a new texting application. Search your available apps for:Verizon MessagesVerizon Wireless- July 2, 2013It has an "auto reply" option. Go into the settings to compose your message and turn it on or off. I just downloaded the application so I haven't really played with it yet but it sounds like exactly what you need.