[Taz-On-The-Road]

The best route is Bangalore->Srirangapatna(Take right towards Ranganthittu. It joins Mysore->Hunsur road at a place called Elwala)->Hunsur->Piriyapatna->Kushalnagar->Madikeri. The roads upto Kushalnagar are fabulous. Just watch out for the mud humps placed by the local villagers which can catch you unawares. Kushalnagar->Madikeri is ok but not too bad either.
The roads around Virajpet aren't great so recommend sticking to the above route. Hope this helps