The way I decoded the script on the world map was by comparison.
Since the seven countries in Ivalice are: Fovoham, Gallione, Murond, Lesalia, Lionel, Limberry, and Zeltennia and each country has a city/location named for it, I was able to match the English names to the script on the map.
From there, I compared the script symbols to the English letters and found a strong match for most of them. It helps that many of the script symbols seem to be based on their English counterparts.
The table below details my efforts at assigning English letters to script symbols. Note that both R and L are represented by the same symbol, which is not surprising since the distinction is not made in Japanese.
