I loved Guam and did find the one gay bar at the time. This was a really long time ago...

If you can't find anything online, then try what I did...I drove up to a nice hotel and asked a cute bellman or valet where the gay bar was. I first asked the concierge (an Asian woman) and she blushed and blew me off.

It is not a very advanced method but there has to be one...between the military and the locals.