It is true that the more of them you eat, the more you'll get used to it. Try mixing in some higher acidity fruits with lower ones in a fruit salad or mixing them with low-fat yogurt. That will help a lot.
I mix mandarin wedges, bananas, blueberries, sliced strawberries with a 1/2 a container of low-fat vanilla yogurt and it makes a great "parfait" type fruit salad. And the dairy will help buffer the acids in the fruits in your mouth.