Most of the free bus service to the Aguilas Park, Water Park, Camel Park and all the other excursions around the town pick up outside several hotels. When you arrive at the airport you will get given leaflets advertising various excursions which also tell you where the buses stop and when. Failing that any of the tourist exchange shops will be able to tell you.
Nearest stop to Garden City for most places will be outside the Bougainville over the road