If you are in good shape hiking wise, do the Saturday run with the Agana hash house harriers. You will see parts of Guam you will never see in the tourist books or hiking guides. Google. Guam hash. On on! Meet every Saturday at 3:30 pm at Pacific business news in Hagatna.
Mangilao is not a place for amusement but education. In this village, you will find the only university and college in Guam. It's about 15-20 minutes drive to Tumon Village - where you can find nice hotels, fun clubs, expensive stores, different amusement centers and more. Did I tell you Guam is small? It will only take you maybe about 2 hours drive around the island.
Guam is blessed with perfect beach weather - temperatures average between 84 and 87 degrees Fahrenheit and water 84 degrees. Tumon Bay, a marine preserve near many major hotels, contains an abundance of marine life.