Yes, it is true, there is some fly fishing in Oklahoma down in the extreme Southeast corner near Broken Bow. I have been down there twice for a total of 3 days and the fishing is what I would consider sub-par, but I want to give it some slack becasue it is Oklahoma and for only being 4 hours from my house it is not bad. In the 3 total days that I have fished down there, I think I have caught a total of 10 fish. Now I have heard stories of people catching 20, 30, and even 40 fish down there a day, but most of those days are on or right after stocking day. Becasue it is a stocked stream, it makes it quite a bit harder to determine what flies to use, mainly becasue since the trout of farm raised they are not used to naturally finding food (Fly's) on their own, they are supplied with food in their pens, probably some form of pellets. Anyway, there are not a ton of fish in the river and a lot of them are not use to the food sorce that we as fly fishermen are trying to give them. Usually when all else fails you just put the weirdest thing in your box on the end of the line and you will get some hits.
Anyway, I will quite complaining about the fact that I cannot catch fish down there and tell you that it is an amazing place just to go and enjoy. The river down there is beautiful and the trees were changing all sorts of fall colors. If you had blindfolded me and sat me down there and told me to tell to guess where I was there would be no way I would have guessed Oklahoma. It was a fun trip.