We also bought the Island Ferry Weekly Passes. After researching for many weeks before we arrived to Ambergris Caye this is what everyone said is a must if you are staying north of San Pedro.
We were at Costa Maya Reef the same week CaroleD and her crew was there (Hey Carole). As the water taxi weekly passes are a good value for going back and forth from the Resort to Town, we also rented a golf cart for the week.
My husband and son drove the golf cart many times back and forth. I only did it a couple of times. We left it in town mostly. We would take the water taxi into town...and our golf cart would be there for driving around town and south of town. We really used the golf cart...
If you don't want to rent a golf cart then buy the Island Ferry Weekly Passes.
If you went on vacation to most destinations you would probably rent a car...So look at it that way. In the long run it would be cheaper than renting a car for a week...depending on how many passes you would be buying.
Research before you go on a trip...could save you money, time and unfortunate surprises or costly surprises.
All the Best,
Ruth