Hi,
I have done this a few years ago, I live in Belfast and got a bus to Derry, I then cycled up to Malin Head Hostel pretty easy, stayed the night and started at Malin Head the following morning. My route was as follows:
Monday 7th June - Bus to Derry then to Malin Head (
http://www.malinheadhostel.com/)
Tuesday 8th June - Malin Head to Omagh (65 miles) B&B
Wednesday 9th June - Omagh to Carrick on Shannon (70 miles) (An Oiche 00353868365220 22euro)
Thursday 10th June - Carrick on Shannon to Kinvara (82 miles)(
http://www.anoige.ie/hostels/doorus-house 0035391637512 17euro)
Friday 11th June - Kinvara to Tralee (98 miles)(Finnegans Hostel - 00353667127610 - 15 euro)
Saturday 12th June - Tralee to Bantry (75 MIles) B&B
Sunday 13th June - Bantry to Mizen head then to Skibareen (57 miles) Bus to Cork Then Bus to Belfast
Total - 447 Miles
I didnt bring a tent and any time i stayed in a Hostel i was pretty much the only person there, not good new for Irish tourism in the height of summer. The riding was easy and the people friendly. This was my second trip in Ireland, the previous year i set out to cycle round the coast of Ireland from Belfast.
Tralee to Bantry was the best day, it had 3 big climbs including Molls Gap, The Gap of Dunloe and The Caha Pass, some of the nicest riding ive done in Europe. The last stretch from Bantry to Mizen was windy, it could easily be done in 5 days but i enjoyed the pace of these days. I was going to cycle to Skibareen from Mizen but i was offered a lift by a woman from Dublin who was dropping her Husband off at Mizen for his Mizen to Malin and as he took a bike and gear out of the car i could put mine in. Couldnt have asked for a better bit of luck.
It can be done more direct, from Kinvara i cycled through the Burren and on to Lisdoonvarna, this allowed me a second chance to see the Cliffs of Moher. I took the ferry form Kilimer to Tarbert and enjoyed a near 20mph average to Tralee. Hostel in Tralee was crap, too noisy for a good sleep but the town was lovely. Theres a nice camp site in Tralee over the river.
I followed the guide on crazy guy
here, even phoned the author when i got stuck in Bantry, the hostel he uses doesnt exist anymore.
As for cycling on the roads, carriageways in the south usually have a full lane sized shoulder which is perfect for cycling on. I really enjoyed this short trip. Motorways are out of bounds but the carriageways and minor roads are perfect
If you need any further advice let me know