The location is 234 E 6th St in Tucson. You can see the buildings still exist and Charlie's was a real auto shop, now out of business. Although the real thing doesn't have the "small town" feel that it did in the movie, being actually in the middle of a medium sized city.
It appears Jonathan Betuel is from this area, or at least very familiar with it. One thing you can't make out from the movie even on Blu-ray but can see in Google Street View is that the building has a name plate indicating it was built by someone named van Harlingen, apparently the origin for the character name "Harlan."