Can anyone tell me where I can find the Hungarian Half-Breed Horse?

The Hungarian Half Bred horse can be found in Mexico. Mexico becomes available after completing "We Shall Be Together In Paradise". The Hungarian can be found anywhere in Mexico, you just have to be lucky.

This video will provide info on how to break the Hungarian Half Bred, American Standardbred and Kentucky Saddler.

Link (if vid doesn't work): link

Took me a while to find this Horse, but I found it not far from El Matadero.

i dont know but i got undead nightmare

I found my one south of chuparosa in mexico

Like what has already been said, you can find it anywhere in mexico. Try looking specifically on the map where there are the pictures of a horse or a herd. I find they don't appear often at night?
(of course, if you have already broken it before, you can purchase it.)
starting the stranger task "Love Is The Opiate" increases spawning- if you are far enough in the game. (By the way you have to of completed the Poppycock stranger task) Start this stranger task and then go to Mesa Del Sol. The horse will spawn around that area. You will have to give the horse to the man, but be sneaky and steal if afterwards.

They are everywhere in Mexico but it's easier to look on your map and look for where wild horses are found and check around there. You have to tame the Hungarian Half Bred before you can buy another.