The road from Ishasha to Bunyonyi is actually REALLY bad, one of the worst. The road from Bunyonyi to Bwindi is almost just as bad. I've travelled all over Uganda and those were actually the worst roads in the whole country. Do you have private transport? Because there is no public transport to and from Bwindi or Ishasha. There is a bus that goes from Bushenyi to Kabale but you'll have to find your own transport from Ishasha to Bushenyi and from Kabale to Bunyonyi.
Another suggestion I might add is to go from Kampala to Kabale on the nice highway, then in Kabale there is a budget travel company that does trips from Lake Bunyoni to QENP through Ishasha www.edirisa.org/queen. It's a really nice trip, but def more suited for the adventure/backpacker sort of person as they do stay in tents to keep down costs. Also from there they do a really nice canoe trek which is a much more "cultural" experience www.edirisa.org/canoe.
I know SW Uganda pretty well... spent a year there... so if you have other questions about the area just let me know, I'm happy to help.
cheers!