My main post covering all of Guatemala is getting long so I'm starting a new post here. The Guatemala City section of that long topic starts here
The only place I've posted about so far is La Estacia Steak House. It is Guatemalan chain with one location next door to the American Embassy
Some useful links
Revue magazine which has some restaurant info for various cities in Guatemala
Que Pasa Antigua expended its scope this month to include restaurants in other parts of the country.