actually, Mac - I'd love to learn to yodel too. I listen to Bill Staines a lot, and love his yodeling, and when I hear him I think I can do it, too - but then when I try, well, let's just say it don't sound like Bill!
It's kinda funny, ya know I've got some range to my voice, and I can sing a bit in falsetto, but when I try to make that transition back and forth, well, it just ain't too pretty!
I have worked at it a bit, and have kept it very simple, and I have improved some, but I believe that is a special skill that requires developing. Good luck.