I have been in contact with some people in Chile via Twitter and asked them the status of their communication infrastructure. Below are some of the reports I received this afternoon.
GPRS is everywhere and 3G is available in the main cities.
They use most of the international carriers such as Movistar, Entel, Telefonica, Claro
The communication infrastructure is getting better. Santiago has no problem. Concepcion has no services and the same with other areas affected by the earthquake.
There are a lot of people in Chile using Twitter. It is mostly reporters tweeting in situ. Some chileans are self-organizing and retweeting as needed. This is how they are looking for missing people.
They think the cell phone grid's will be working more than 75% in less than 1-2 weeks.
Sophia