Probably right, melons take a lot of water in proportion to the harvest you'll get. Best to let someone grow them for you where there is enough water to size them up. Especially watermelons are water hogs, and then you're growing a lot of rind that you won't eat, too.
You could probably grow Dragon Fruit really nicely there - they grow on an epicactus, don't need a lot of water.
Dragonfruit (Selenicereus monacanthus)
