Geelong is the practical eastern gateway, with Torquay about 25 kilometres farther south. From Melbourne, allow around 90 minutes to reach Torquay before the scenic driving really begins.
Public transport can get you to some towns, but the Great Ocean Road is much better with a car or a well-planned tour. Distances are deceptive: the road is slow, curving, and full of stops, so build an itinerary around time rather than kilometres.