Lack of buses is not a problem. Here's how it works. You will disembark from whatever form of conveyance you travel on from Ruhengeri at the Cyanika border post. Within, I don't know, nanoseconds, you will be approached by an assortment of mostly young men, all advertising their services for transport arrangement from the border to Kisoro. You can grimly put your head down and attempt to ignore them as you walk into the little immigration hut, or you can have fun and negotiate with them, arrange your taxi and get your chosen winner to carry your luggage throughout the border crossing process. After your chat with the lovely gentleman at the Rwanda border post (at least the one I had was nice) and the requisite passport stamp you walk to the Ugandan post - this walk may take you 30 seconds - once again you will be accompanied by the coterie of young men (if you have not yet made your transport selection). You fill out your form, pay your visa fee, get your passport rubber stamped and you're officially in Uganda. Within 15 to 30 seconds you will have walked to your chosen transport. If you have avoided making that selection there should be an assortment of vehicles, aka taxis (don't ask for a license) all more than willing to take you into Kisoro. You will choose one of these. Pick whichever one strikes your fancy. Depending upon the driver it will take, oh, I don't know, several minutes to drive you to dingy downtown Kisoro.
To spend the extra several hours it would take to go to Kabale and then take the road from Kabale back to Kisoro (and when you finally take that road you will know what I mean) would just be insane. Even with slow traffic (maybe), lots of people crossing the border (unlikely) and a slow taxi driver (ha ha) the journey from Ruhengeri to Kisoro is probably no more than an hour and a half.
