We are planning trip to Australia and would like to drive the Great Coastal road leaving from Melbourne.
Does anyone have any suggestions as to how long we should allow for exploring this area?
Can it be done in a day or should we allow longer?
Any suggestions of places to stay along the route?

The correct name is the Great Ocean Road, and it is an extremely long trip to do in one day. I suggest you leave Melbourne very early, and spend a night in Apollo Bay (lovely YHA flash-packers there), and then complete the road as far as Port Campbell or Peterborough the next day, and then straight back to Melbourne via the highway. A second night on the road is also rewarding, and you can avoid rushing.
Also, note that the Great Ocean Road is closed at the moment between :Lorne and Apollo Bay ... a severe bushfire went through on Christmas Day, destroying 118 homes / holiday homes and burning a lot of bushland. You would expect it to reopen reasonably quickly (within days or weeks).

Thanks so much Ian.
Really appreciate your reply.
We are in Canada and re planning a trip to Oz in March/April with a couple of weeks in Tassie followed by a few days in the Melbourne area before heading to Perth to visit my sister.
While in the Melbourne area we would also like to visit Philip island and wonder if it would be advisable to take a tour or attempt to drive there in our rental car. Of course we are unfamiliar with the area and might spend quite a chunk of our few days with route finding!
One last question - any suggestions for reasonable accomodation in Melbourne??
Thank again.
Anne & Stan

Driving to Philip Island for the penguins is easy stuff, big roads and not hard to do and all that. PI has more to offer than just penguins and is a nice place and that would be a reason to drive. The advantage of doing a tour is that dusk is at about 7.30 pm so you will be lucky to be leaving at 10pm or so which won't put you back in Melbourne proper until midnight so you might prefer to be on a coach. The downside is that you are running to someone else's timetable. The short answer, drive.
Where to stay in Melbourne? I've made a habit out of staying at the Albany Motel in South Yarra. There are several reasons for this. 1) Prices are usually pretty good. 2) There is free wi-fi (which is usually reliable). 3) It is easy access to central Melbourne. 4) There is some free on-site parking. 5) I've found the rooms to be good (try to get one in the main building rather than a 'US Motel' style overlooking the car park) and staff to be mostly good. The parking and wi-fi points are somewhat unusual this close to central Melbourne and for this standard of hotel although I have battled with wi-fi on one occasion and have had to grab the last parking spot more than once and seen other queuing in the morning to avoid on-street parking restrictions. Do your own research about the place online.
I did it in two days and it felt really rushed. If I would do it again, I would at least take 5 days. So many nice places around there.
The downside is that you are running to someone else's timetable. The short answer, drive.
If you already have the rental car, then I concur with Mark ... might as well drive rather than take a tour. In fact, you could save up to a day by combining the Great Ocean Road (GOR) and the penguins - and have a better trip into the bargain.
So, reverse your trip and head out along the highway west of Geelong (have a map?) and stay at Port Campbell, or if you go a bit faster, Apollo Bay, but it is the stretch between Port Campbell and Apollo Bay that warrants the most time, including side-trips to the Otway Fly (an elevated forest walk), and Triplet Falls, a lovely one-hour short trail.
Then drive the coast road to Torquay - including seeing Bells Beach, one of the world's surfing hotspots - and then through Barwon Heads to Queenscliffe on the Bellarine Peninsula, for the night. Again, a very nice resort town, and the Inn is good to stay in (not the Hotel, which is upscale and expensive). Then take the Sorrento car ferry across to the Mornington Peninsula, and take all day to drive to Phillip Island for the fairy penguins.
Then either stay locally (or somewhere like Frankston along the Nepean Highway), or drive back to Melbourne late. I think this suggestion adds a lot of value, compared to doing the GOR and the fairy penguins separately.
In Melbourne, it depends on whether you need parking, but look at the Pegasus Apartments, or perhaps one of the Oaks properties. Friends of ours have also stayed at the very central City Gardens Motel in Little Bourke Street, and they recommend it (although I doubt there is parking).
Note that if you do wish to do the fairy penguins (or GOR) via a tour, there is a Half-Tix shop in Melbourne Town Hall, where you can buy discount tickets (cash only, for the following day only) - so a $149.00 ticket might be $79.00.

Thank you so much Ian.
We do appreciate your response with all that information.
Now we need to get on with planning our trip.
We leave Canada in March and have 4 1/2 weeks of which we plan to spend 2 weeks in Tassie driving around in a campervan. We hope that with 2 weeks we'll have time to do quite a few things as well as some hiking.
Then one week in Perth visiting family before flying home.
Haven't rented the camper yet and hope that there will still be availability.
Thanks again for all your tips on a route.
Anne & Stan
Ian, please correct me if I am wrong (which I know you will do) but don't you have to go well past Apollo Bay/ Port Campbell if you wish to see the likes of the 12 Apostles and the other wonders of the shipwreck coast?
I haven't done this for a long time long time but you do need to go down as far as or nearly as far as Allansford to get to the 12 Apostles then work your way back towards Apollo Bay/Lorne/Torquay /Barwon Heads/Ocean Grove/Queenscliff/Sorrento etc.
Not a correction, msscanna, just a clarification.
I was suggesting they head west from Geelong and therefore via Colac to Port Campbell the first day, and then take all day to drive from Port Campbell east towards Apollo Bay / Lorne / Torquay.
Yes ... you certainly have to go west and well past Apollo Bay (if driving from Torquay rather than Colac way) to see the very best of the GOR. But by the time you have reached Port Campbell, that's pretty much it, at least if you go a bit further and see London Bridge and the Bay of Martyrs, but they're not too far west of PC.
okay just to clarify that bit more for the op - if taking the Princes Highway head to either Colac or Camperdown to get to Port Campbell to lead you into the area of the shipwreck coast and 12 Apostles. Heading as far as Allansford/Warrnambool is probably going a bit too far. Just remember though, the roads can be narrow, windy and sometimes a kangaroo/koala may get in your way.