Firmness is the key to this salad — you want the mangoes and avocado to have character. The mangoes shouldn't be fibrous and the avocados should be uniformly green and not mushy at all. You should have to bite into both.
Two alternate versions of this salad work well too. Thinly-sliced Fresno peppers are a nice touch of color, and if you can find them, Champagne mangoes take the salad to the next level — they're a little more tart than sweet. You're going to get some sweetness from these shrimp anyway.
Also consider grilling the fruit. A little char on the mango, avocado, and tomato will bring another whole dimension to the salad.
Click here to see 8 Fresh Fruit Salads.