The best sauna for foreigners is probably "24". There are several locations, but the best is the Shinjuku location. Ueno is pretty good too. I've had lot's of fun at both. The one in Shinjuku is just soooo conveniently located. in the heart of the gayest area in Tokyo! haha
I've never used King of College but I used Tokyo Kids once. The guy who was working the entrance spoke English and he was available, but I ended up choosing another guy. I went in prepared and had a few of my wants/likes translated so my expectations for the encounter were relatively clear. Being able to communicate is nice but I wasn't there for conversation either!
I recommend KOC or Tokyo Kids if you're short on time or if you are after something specific and you don't want to waste time. Otherwise, going to 24 (or another sauna) or using an app like Grindr will be more rewarding. You might have to do some "hunting" but you will have a lot of fun. 24 has a lot of variety (Japanese bears as well as twinks, younger and older guys, along with many foreigners), plus you have the shower and steam rooms, group rooms and private rooms (those cost more though). The group rooms have open spaces, which can be fun and even lead to orgies, but there are "bunk bed" style play areas in the group rooms that offer a little more privacy - not so much on the top but the bottom bunks are very dark.
I can't comment on Kyoto. I only did a day trip there from Osaka to enjoy the sights.