Yes, Carlsbad Caverns is a long way from Las Cruces. Approximately, 200 miles to the Southeast. But, if you are RV'ing Southern New Mexico, both White Sands National Monument (45 miles east of Las Cruces), and Carlsbad Caverns are two of the "must sees."
If you are driving Las Cruces to Albuquerque, you can avoid the boring I-25 (and it is boring most of the way), by driving the old U.S. highway much of the way. LC to Truth or Consequences via NM-185 for instance. You get to see the smaller towns this way, such as Hatch, the home of the world's best chiles. From Bernardo on I-25, you can drive north through Belen, Los Lunas, and Isleta Pueblo into Albuquerque on NM-314 I believe. Exit I-25 north at the Bernardo Exit, then continue north across US-60, on the two lane highway.
Once you get your itinerary finished, we can be of more help with specific recommendations.