This is the season for them down here, most are larger than a big man's fist and they are very refreshing, kind of sweet but not super sweet. I like them a lot and they are great in a fruit salad. Bazillions of tiny seeds in them but they are crunchy and you just eat them. They also make a very good fruit drink, blend the fruit, strain, add sugar if desired and a little water - delicious.
I won't tell you how cheap they are, sold on every corner.
Edited to add, the way I got some of my pitaya (Dragon Fruit) was by following the advice of the locals. If you are eating one that is very sweet and good, save a tablespoon or so of the pulp and spread it on a wall near the base. The seeds will sprout and because they grow so rapidly it will run up the wall.
The most convenient pitaya I've seen growing here was in the hollowed out base of a dead palm tree. It was only about 4' off the ground and the plant trailed down almost immediately, no where up to go. The fruit was reachable and as the owner said, it was all on his side of the fence!
