Minho lets everyone sleep for about four hours, and when they wake up, they start walking toward the city. It's pretty darn hot out, so running would take up too much energy.
Time passes, and it's nightfall again. Thomas figures they'll reach the city the next day. Then he falls asleep. Again.
This time, Thomas dreams about when he was 10 years old. In his dream, he's with Teresa, and she's trying to get him to speak telepathically. She gets frustrated that he can't, and she refuses to talk to him regularly until he can speak telepathically. Yeesh, tough coach.
Of course, Thomas does finally get the hang of it.