Strange that the OP didn't think to book Phoenix-Aguascalientes on CO (with a transfer at IAH)! A lot less hassle I'd've thought.
Anyway, ETN offer probably the best bus service back to Mexico (Terminal Norte). The fastest journey time is four hours. The roadworks to the airport should be finished by November, although good cab drivers know how to bypass them; so allow another hour to make your check-in time.
ETN can be booked online.