The shuttle service is incredibly expensive given you are max 10 min from the airport. In the US, it would be free at that distance. A taxi is cheaper if you are a party of 2 or more. Best to rent a car as you will need it at the Marriott.

This hotel is a dog. We just stayed there last month en route to Palau. It is in dire need of renovation and frankly should be a Ramada, not a Marriott. The local paper had an article about the hotel with the manager admitting it does not meet the Marriott brand standard. Understatement. We faced on the quiet side with a view of a trailer park next door. The beach access is a joke - walk through a chain link gate to a small beach with 4 lounges! The concrete around the pool has been installed by many incompetent workers over the years. Very sharp pebbles in the coping so you need flip flops or you will kill your feet. They were cleaning the pool so long we never got in it. The rooms are grim, old wall paper, baths, etc. Dirty carpet. You are NOT in any sort of action area and would need a rental car. There is nothing much on the street nearby. Marriott should have more pride.

A woman in the Star Alliance Lounge at the airport told us the Hilton was worse. Not so. The staff is ditzy but the hotel, at least in the status tower, was really nice. Renovated room, nice view, great mattress, etc. Price the same as the Marriott.

I would not vacation on Guam other than a single visit to see the war monuments and locations. It is a poor version of Hawaii. For a cheap Asian beach vacation, go to Kuantan in Malaysia and stay at the Hyatt.