how is you, glad to see uni-newbies
anyway, i<ve heard that the best size wheel to learn on for someone your stature would be a 24 inch, but now your choice of size would depend largely on the type of riding you wish to do.
i do some mountain unicycling, the best tyre for this sport would be a 26 inch, you could still learn on it, it's not that bigger than a 24 inch.
but if you want to do trials and freestyling and stuff like that, a 20 inch might b better, it's a bit smaller but you should still b able to learn on it....i'm 6 feet tall too, and learned on a 16 inch.
but i think the best syze is 26 inch, it goes faster and you ca still do some trials with it, it's a bit harder, but still possible.
anyway, i can't tell you more
but you can go see these sites:
and maybe unicycle.org
that is all