There were actually around 50 checkpoints of the rebels that the missionaries had to go past.
Over the course of the filming in Ghana, the cast and crew actually ran into real LDS missionaries several times between shots (this usually came to surprise and confusion of the real missionaries because the actors' white shirts were so dirty and their tags used the LDS logo from the 80s). Some of the real missionaries were from the US, so when American members of the crew recognized them, they gave them rare treats like cans of Coke, Pringles, and Famous Amos Cookies.
The verse on the back window of the red car the missionaries used reads (Mark 9:24): "And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief." It was chosen as part of the film's theme of moving forward with faith despite the adversity and challenges that seemingly lie ahead.