Yes they should promote both for combat and domestic disaster relief. If they don't help us out here at home then they are not truly serving their country with pride, and love the way they claim they do. We are not always at war with every country in the world.
The National Guards main focus is the domestic front, but in times of conflict every person in the service and even those in civilian life must be prepared to answer the call to service. The National Guard has been invaluable in helping with disaster relief over the years and they should continue to assist in this area.
The National Guard should stay home and help with domestic disaster relief. They are soldiers in training, and if they should get called into overseas combat roles then they should become full-time members of the armed forces. Overseas combat should be left up to special operations instead of large invasion forces as we have seen from the debacles in Iraq and Afghanistan.
It is my opinion that the National Guard should serve only in domestic disaster relief as opposed to serving in combat overseas. The other branches of United States military are largely sent overseas for combat. For this reason it would be imperative to have some form of military that consistently occupies American soil such as the National Guard does.