Well I have heavily planted tanks, so that might be the key, but I have lots of fry survive to adulthood with the parents.
My survival rate skyrocketed with I began crushing some flake, mixing it with water, and pouring it into the tank so that the fry don't have to come out into the open.
All fry know to hide, but if the only way to eat is to come out- they come out.
I keep snails, ghost shrimp, adult guppies, 1 platy, and fry all together. I have no idea how many are eaten, but I know that I've never had a problem with not having 1-2 more adult guppies per week.
I also don't clean my glass. There's very little algae, but the guppies eat it, so I like to leave it for the fry.
Java moss, Guppy Grass, Hygrophila Difformis, are all easy plants that hide fry well.