To me, Carl’s is a piece of California lore, and a ok burger as well. That said, I would like to take a moment to pitch Springfield MO as welcoming home for In-and-Out Burger should they wake up as Carl Karcher Enterprises did. ;)
Dallas (or more likely Plano or the mid-Cities) is a more likely location for In-n-Out. There are about 20 in the Metroplex and another 7 scattered down I-35.
Phoenix would be another option, with 17 locations and another 7 down I-10.