Does anyone know if US cell phones will work in Guatemala? Or will we need an unlocked phone and a chip?

You can purchase a Sim card from the cellular providers in Guatemala. The stores are quite prevalent. AT&T phone worked fine.

It should work, but your roaming will be out of this world. You can pick up a sim if you want, or just pick up a prepaid phone down there. They are very cheap and the cost of calls back to the US are cheap.

If you are planning to use your regular US phones with the regular US card, then they will probably work on roaming. Cingular though doesn't really work all that well. US cell phones that have not been unlocked will not work if you insert a card from a different company that is not the one you bought the phone from. So I would suggest traveling with the unlocked phone and getting a card here, or buying a really cheap pre-paid phone once you get to Guatemala which you can always sell back. I'm not sure if you can buy just the cards, but I'm pretty certain you can. As for cell phone companies here, I would definitedly suggest going with Tigo whatever you decide to do as they have the most coverage and rates. Oh, and the pre-paid phone should work all over central america.

I DON'T THINK SO MINE DID NOT WORK. WELL IT WORKED BUT YOU CAN'T MAKE CALLS ANYWHERE

I have Sprint and mine worked just fine down there, the dialing to the U.S. is different tho, I can't remember exactly right now but I think it was 147-130 then the U.S area code and number u wanted to call. Sorry I can't remember the digits right now, but like I said, my cell worked just fine down there and it still works here in the U.S. Good luck and be CAREFULL with cells down there, u can get killed for one, LITERALLY :-s