I have just been at this HGI and the shuttle schedule did seem erratic and I had a long wait at the terminal upon arrival even after phoning the hotel. There is an option of using the free around the airport shuttle not connected to the HGI which as a previous post said stops just behind the hotel and runs frequently. To use this just look for the large orange bus called "Navatta" and has shuttle on the destination board. There are bus shelters in front of all the airport terminals for this. The stop behind the hotel is number F2 "Cargo City". Then there is a short bricked pathway to the front of the hotel.

All of this does take time and you could save a lot of that by staying at the Hilton from which you can easily walk in and out of the terminal. One advantage of the HGI is the free internet access in the rooms compared to the very expensive service at the Hilton.

Hope this info helps.