The map shows the estimated 3G coverage services in America for 2012. Guatemala stands out (note that Colombia and Panama also have large coverages, but not the extent of Guatemala).
The map is from the case study "Privatization of Telecommunications in Guatemala: A tale worth telling," by Sabino and Leighton (May 2012).
The following charts, also taken from the case, are telling:
The authors also argue that prices have decreased substantially.
I reported a similar reform with also impressive results in Haiti. See here. The phone and 3G coverage have increased largely in Haiti, not to the extent of Guatemala, but it is rising. The Haiti reform happened in the past two years. Similar reforms have happened in Africa, with great results.