Car Rental on Guam is the Only Choice
There are a few methods of traveling in Guam. You can hitchhike but I wouldn’t recommend it because unlike Hawaii’s wide highways, most of Guam’s roads are narrow and unforgiving. It just wouldn’t be safe. Secondly don’t wait at a public bus stop because the bus just might never come. Thirdly if you’re staying in a hotel depending on the hotel shuttle service is available for a fee unless it’s to the airport. Taxi’s are very expensive in Guam. A ten mile trip can cost you $50 USD or more. Lastly I would recommend a Car Rental on Guam which would be the most freeing choice to glean out Guam’s beautiful spots.
If you have a good friend or relative in Guam than of course transportation isn’t a problem.