Goofs

Casey doesn't take out her iPhone to record Kenny's spider bites until a moment before he collapses, yet the video she posts on YouTube includes David and Rose convincing him to pull his pants down and show them the injury and you can hear David clearly say, "We can't stop!" all of which happens long before he collapses.

When the DEA raids Brad's office Brad and David can be seen protecting themselves from falling glass and the office doors wide open behind them. The next shot shows the doors being kicked in.

Casey begins to record Kenny singing "Waterfalls" but in the next shot her phone is nowhere in sight. She's not holding it up and it's not in her hands (she's clapping.)

When Kenny gets bit by the spider he pulls down his pants. It shows him from behind with his pants at his ankles. In the next shot where he passes out his pants are pulled up.

Kenny's watch disappears when on the sidewalk outside the Albuquerque Sunport, just before the Millers get the RV. It appears in all previous and subsequent scenes.

The Millers' RV is being towed with only a chain, so someone would have to be in the towed RV to apply the brake when necessary (e.g. on down grades, or when the lead RV brakes) or the Millers' RV would roll right into it.

As they reach the border checkpoint on their way out of Mexico the Fitzgeralds pull up next to the Millers in their RV and Don Fitzgerald rolls down his window to talk to the Millers despite the fact that the Millers have an RV with rubber-sealed passenger side windows that cannot roll down or even open. The RV the Fitzgeralds drive also has a permanently sealed rubber-gasket passenger side window, yet their RV window is simply gone when Edie Fitzgerald talks to the Millers by the roadside where the Millers' RV is broken down.

When they are getting checked by TSA at the airport leaving Denver, they show each of their licenses. Casey's license has the Zip Code 82012. However that is a Wyoming Zip Code; Denver is 802xx.

When Don tows the Miller's RV to the repair shop, he pulls up close to a wall in front of their RV. An experienced driver would leave turning room in front and not get into a "backing situation", especially when towing a disabled vehicle.

Rose chastises David for not thinking, and for driving up a 10% grade (which is presumably what causes the engine to run hot enough to rupture the radiator hose). But the grade they're driving is nowhere close to 10% (which means 10' rise for every 100' forward); it's closer to 5%, which would still be a strain for a motor home that size.

When David is talking on his iPhone in the garage, his iPhone is clearly locked the whole time. The lock screen is visible when he hands his phone over to Pablo.

At the start of the movie, David is watching YouTube videos. When it displays the laptop, the video is playing but the pause/play button displays 'Play' which would only be seen if the video was paused, however the video is clearly not paused.

Casey tells Rose that Kenny has never kissed a girl before. This is incorrect as they just finished kissing each other.

With every scene the motorhome is in, the audio being played signifies it is powered by a diesel engine and has air brakes. There are numerous scenes in the movie when you can see the V10 emblem on the front corner of the motorhome. The motorhome is actually a Ford chassis with a Triton V10 engine and has hydraulic brakes.

When the Millers arrive in "Tucson", they are very obviously exiting the Albuquerque International Sunport in New Mexico in the next shot. Additionally, the following montage of the RV driving through the desert is implied to be in southern Arizona, yet the scenery is clearly that of New Mexico, particularly central and northern New Mexico, nowhere near the Mexican border.

How did Rose get on the flight to Tucson? Assuming she was able to go back to the strip club and retrieve the plane ticket David bought for her, she would have had to buy a new one with her real name on it.

Kenny was feet away from Casey when David negotiated how much he'd be willing to pay her for joining him and Kenny. He is closer to Rose when she sets her price. He (& Casey) then sounds shocked when he hears Rose and Casey complain about how much they'll receive in contrast with how much David will get.

When the Millers are stopped at the carnival, Rose tells David that her real name is Sarah. At the beginning of the film, David very clearly sees Rose's eviction notice that was left in his box by mistake. If you look very closely, you'll see that the mail was addressed to "Rose O'Reilly." Rose would have had to provide legal ID to rent the apartment, in which case the mail would have been addressed to "Sarah," not "Rose," in which case David would have known her name from the beginning.

Despite being a drug enforcement agent, Don Fitzgerald is unable to smell a bale of marijuana from 5 feet away.

In the beginning of the movie when David and Rose are at their mailboxes, David gives Rose a bill of hers that was mixed in with his mail. Later in the film, Rose tells David that her real name is actually Sarah. The bill would've had her legal name on it and not her stage name.