That Today show link seems to have pinned down pitahaya. Today I had something similar called Chan.
This was a bright cherry color with the same type of tiny pulpy seeds as pitahaya. I asked the waitress if it was the same thing and she said no (different restaurant).
Chan is very pleasant. I did give googling this a shot, but give me a break ... Chan ... I'm surprised I didn't break google. There are quite a few 'fruit', 'beverage', 'recipes' by people with the name of Chan. There actually is someone NAMED Chan Fruit (my initial search).
I did find this limited info though ..
Some of the more unusual frescos are horchata (made with rice flour and a lot of cinnamon) and chan (made with the seed of a plant found mostly in Guanacaste -- definitely an acquired taste). The former is wonderful; the latter requires an open mind (it's reputed to be good for the digestive system).
But that cant be right. It is a really pleasant taste that anyone, even steak and potatoes people would like. You don't need to 'aquire' it.
Any clues? Again, if you see it on a Central American menu, order it. It is delicious and pretty.