Six of us from the company I work for had flown into Albuquerque, New Mexico - about a 5-hour drive distant from the town of Carlsbad. As a result, we rented two trucks for the journey southeast to almost the Texas border, since we all had luggage as well as work gear with us for our three week stay in the area.
I took this Dodge Dakota AWD for the 27-mile drive from the city of Carlsbad to the National Park via Highway 62/180, with the last seven miles being on a scenic road inside the NP. The truck worked great and air conditioning was essential in the desert heat. The vehicle I rented from National cost US$1550 (including extra insurance) for three weeks and gasoline was running at just under US$4 per American gallon (the least expensive grade) at this stage of the up and down oil prices.
As said many times prior, walk the trail for the best part of the tour, inside and out ! Be sure to have your little audio recorder handy, as there are numbered stations along the way to listen to if you're doing a self guided tour.