Just rewatched this masterful film, No Country For Old Men. A few things came to light from having watched an interview with the Coens, Brolin and Bardem on YouTube.
A couple things, though, continue to puzzle me.
After Moss goes on the lam following his boneheaded decision to take the drug runner water (dude!!!!), he sends Carla Jean to her mother's and goes off to try and throw any pursuers off his scent. Chigurh, upon breaking into Moss' trailer, finds a phone bill that leads him to Odessa, TX, where his mother-in-law lives. That all is fine.
What is less clear is this: after Chigurh gets the transponder from the two "managerial types" (and kills them), the gadget isn't close enough to the money case to register a blip. From the movie, I can't even figure out where Moss goes to the (first) hotel room, or even how he decides where that is. However, there's a brief scene where Chigurh drives over a road bridge and past a sign that only shows Route numbers, (and tries to pick off a bird with his silenced rifle as he crosses the bridge). This would seem to indicate he knows where he's going. But, with the transponder not giving any clues (until he's just down the street), how does he know where to go, to get close enough to get that blip? And for that matter, how do the Mexicans "squatting" on the room know?
More on this I read the screenplay, and found a little more info, but not enough to categorically answer the question. When Moss puts Carla Jean on a bus to her mothers, he tells her he's going to borrow a car from Roberto. (Moments) later, Chigurh puts in a call to Roberto's Automotive (presumably from the phone bill). However, the phone bill would not include calls made within about a week of its appearing in Moss' mail slot, so how would that tell Chigurh a possible location for Moss to flee to? He found Carla Jean's mother from the frequency and time length of calls to Odessa, TX. Still not sure how this "leads" Chigurh and the Mexicans to wherever the first hotel is.
And also, when Moss gets to that first hotel, he takes a cab. Seemingly, he never takes possession of Roberto's car.