Fortunately, Las Cruces and New Mexico consider their night skies to be a natural resource and have enacted codes to preserve them. Since 2000, all new outdoor lighting in Las Cruces has been required to utilize full cut-off designs. Existing outdoor lighting (installed prior to 2000) must be brought up to code by 2010.
Like the switch to energy-efficient fluorescent lighting, there will be some costs incurred in upgrading your outdoor lighting, but these expenses will be more than offset by the cost savings that the newer, more energy-efficient lighting designs will offer.
What distinguishes well-designed outdoor lighting from poorly-designed lighting? Several examples of good and bad lighting designs are illustrated to the right. More examples may be found here.
You can help! Make sure your outdoor lighting (and your neighbor's) complies with State, County and City codes. The Las Cruces code can be seen here.
Replace inefficient, energy-wasting and light-polluting lighting with cut-off lighting. Ask lighting resellers such as Home Depot whether the lights they're trying to sell you are in compliance with the city's lighting ordinance.
Remember to turn off lights when they're not needed.
An excellent resource to learn more about light pollution and what can be done about it is the International DarkSky Foundation.