The iTunes App Store on my laptop computer opens in English. The credit card tied to my iTunes account is a US address. My iPad an I are in Mexico. My iPad is set to English for language in the general setting, but when I open the iTunes app on my iPad (iOS 6.0), it is all in Spanish with no way to change it. What do I do to get the iTunes app to appear in English?
if you taking about the iTunes Store navigation, this will reflected our current store country (I presume Mexico as per iTunes terms and condition you should match the iTunes Store country with your billing address).
You can still go on https://appleid.apple.com/account/manage and select your language.
iF is the actually application itself you want to go on your IOS devices : Settings /General/Language&Region/ and select the correct langue but I don't think that the issue here.