Rent a Wreck is the way to go for the very reason Karen mentioned. If you do need a backup plan, you can save some airport car rental surcharges by renting from one of the 3 car dealers. If you're catching city buses, the Valley Express drops at the Nugget Mall, right in front of all 3 car dealers. I would download the bus schedule if you were planning on that method.
The only way to keep everyone happy is to delete my signature completely.
If anyone wants advice from a life-long Alaskan resident, please don't hesitate to ask.