Since I don't have sand I can't address that in particular. I have heavy clay which I try to amend with compost but eventually it is always heavy clay again.
For that reason I have separated my lilies from the JIs, at least some of them and I will move more lilies in the fall. I have really been putting a lot of water on the JIs this year and even "invented" a thingy to help the water go deeper, otherwise it tends to just run off into the neighbor's yard and water his weeds from h&*%^.
One lily that will not tolerate a lot of wet is L. auratum; I don't know about its hybrids. I purchased a bulb and it didn't last a year in my wet clay.
A lily that needs moisture (and acidic soil) is L. superbum ("Swamp Lily", sometimes available from B&D Lilies).
Most of your ordinary garden lilies will tolerate a dry period like we have in the Northwest every summer but summer water won't harm them as long as the soil drains well, especially if your clmate is particularly hot.
