Why does it take so long for a program like Mapdroid to use the GPS to track you on a map
This shows the difference between AGPS and GPS. AGPS (Assisted GPS) uses a small amount of mobile data to establish a rough location fix (about 1km-100m accuracy) based on the cell towers near you. This gives a faster initial location fix than just GPS. Since you had roaming disabled, AGPS wasn't available and getting a location fix on just GPS can take a while, especially on some firmware versions of the Galaxy S.