Continuity mistake: In the scene where Kenny feels he's been bit by a spider on his privates and run off the bus with everyone following after him. Kenny then pulls down his pants so they can look at it. Throughout these scenes, his pants are supposed to be pulled down. Right at the moment Kenny faints from the bite, you can see that his pants are pulled up and buttoned.
Factual error: When the Millers' RV breaks down and it gets towed by the Fitzgeralds' RV, the two are connected by a tow rope. There is no one in the Millers' RV steering or working the brakes. The RVs would crash into each other the first time the front one slows down, and the Millers' RV would not steer properly to follow the Fitzgerald's. Also, when we see in the Fitzgeralds' side mirrors, we don't see the Millers' RV being towed.
Continuity mistake: In the scene where Jennifer Aniston has finished giving a striptease and the Mexican Drug Lord, Pablo Chacon falls from the chair because of the steam on his face, he is shown sitting in front of the RV, but he falls right on to it. Then when Will Poulter drives the RV in reverse, Matt Willig is shown colliding with it, but Pablo Chacon is out of the picture. (01:18:10 - 01:18:50)
Continuity mistake: In the scene near the end where Pablo Chacon is holding a gun to Melissa's head and telling Don Fitzgerald to give him the gun and mug, we see the gun pointed towards Melissa for the front shot, but in the next shot where we see Don giving Chacon his gun and mug, the gun is pointed towards the ground. (01:44:10)
Continuity mistake: When the Millers and Fitzgeralds are playing Pictionary, Melissa draws a little stick figure with a hat, the camera cuts to Kenny for his line, when they cut back to Melissa the stick figure with the hat is missing. In fact all the drawings are slightly different. (00:57:25)