Can I buy an iPhone 3G at a apple store IN THE U.S and use it in Mexico on Telcel (They sell iPhones there but their really expensive to buy in Mexico) without having to unlock it?
Yes, you can get an unlocked iPhone directly. If you feel its a way too costly, you can opt for a locked mobile and then unlock it through reliable third party unlocker, Classicunlocking.com and then swap networks in your iPhone 3G.