I make this salad too...I usually make it with pineapple tidbits instead of crushed pineapple, and I do drain it. I also like to add 2-3 chopped granny smith apples to add a bit more fruit to the salad. I always get asked for the recipe when I make it.
If I am taking it to a smaller group, and don't think it will all get eaten, I will keep the pretzel mix separate and serve it over the top of the salad, rather than stir it in so leftovers aren't soggy.