It's a very personal decision for you whether or not to obtain a passport for yourself as part of your Marine's pre-deployment preparations. To help you make that decision, it's helpful to understand that it would be extremely rare for a family member to travel abroad due to an injury, illness, or other emergency. If the need for a passport did arise, the USMC would assist a family member in obtaining one as quickly as possible.
However, if you have a need for a passport in the next 10 years (passports are currently valid for 10 years from the date of issue) other than your Marine's deployment, you might want to consider it. Generally speaking though, this is an expense most families do not have to incur.
Passport applications are available at most US Post Office facilities. For additional information from the USPS about obtaining a passport, including fees and a passport application form, please see: