I lived on Guam for 4 years, it's a nice place to visit but not a nice place to live. What branch of the millitary are you in? Air Force or Navy? The Naval base there shut down I thought? We lived on the Air Force base (they have 2, Anderson where mostly officers live and Andy South where it's more enlisted).
As long as you do all your shopping on base, you'll probably be ok (the BX and Commisarry keep the prices reasonable, but off base you'll pay $9 for a jar of peanut butter).
I hope you're not a big fan of Milk, that was a big surprise when we moved there, didn't think about how there weren't really any dairy cows on Guam, so they have to ship all of their milk in, and they add funky preservatives to make it last the boat trip and it tastes awful. When I got back stateside, the first thing I did was have a big bowl of cereal with real vitamin D milk (funny the things you miss).
The natives in Guam are called "Chamaros", but there aren't a ton left. I would actually estimate that there are more Philipino's than Chamaros there. Get ready to hear "Howley" alot. They have the chamaro version of "Aloha", but I can't remember how to spell it, but it's pronounced "Hoffa Day".
There are some nice things there (there are some nice beaches and some fun water activities), but there is a reason they call it the poor mans Hawaii (everything is dirty and vandalled).
I don't remember you mentioning you have any kids, but if you do, the schools there are horrible (when I was there, there were no DOE schools, so it was all off base, and they have a really bad problem with gangs). They get a lot of their tv piped in from California so everything is bloods and cryps there.
Sorry to be so negative, just some experiences.