Truth or Consequences sits on Interstate 25 about two hours south of Albuquerque and an hour north of Las Cruces. By car is the only practical option for most visitors — there is no train service and bus connections are limited.
The nearest major airport is El Paso International Airport in Texas, about two hours south. Albuquerque International Sunport is about two hours north and offers more domestic connections. From either airport, a rental car is essentially required.
If you are coming from Albuquerque, the I-25 drive south through Socorro and past the Very Large Array (visible on clear days from the highway, off to the west) is one of the better stretches of interstate in New Mexico. Exit 79 takes you directly into downtown T or C.