So long as you are willing to be bound by the laws of the United States and you follow the instructions provided within Standard Legal’s Last Will and Testament legal forms software package, you can certainly create a valid Will while living in a U.S. Territory.
Standard Legal offers Wills that are “self-authenticating”, meaning the signature of the witnesses validates the Will. But a Will is further validated if signed in front of a Notary, who would also sign and stamp the document upon seeing your signature. So it may be in your best interest to find a notary in your location.
You also may wish to review any laws specific to your city or region as they relate to estates and their distribution.