Saving brassica seed

I don't think there are too many kale varieties to worry about cross pollinating. Unless you've got curly kale, red kale and tuscan kale in the same area. Then I could see some unusual varieties popping up.

Sorry, I missed your point first time around. Yes, all the brassica family will interbreed with one another unless you've taken specific care to avoid this. Which I'm guessing you haven't. You could always plant a few seeds to see what you get, but for the most part, I'd buy specific seeds so you get what you want with no surprises. The only way they're likely to not interbreed is if the crops are over 1,000 ft away from each other. That sort of puts allotments out of the game