Personally, I would keep your workshops near the top of your fortress, where the sand is, that way you won't have to clear out rock for stockpiles and such.
Workers don't really have impressions from the quality of certain areas, or at least, they get no negative thoughts from working/being in sandy areas.
As for bedrooms, make sure they are z-levels above or below your workshops, as dwarves can become afflicted by noise, plus, if you do it below, you can smooth all the rooms and make them nice, beware however, if you have the economy turned on then nice rooms can lead to homeless dwarves once the economy kicks in.
I myself like to have a fortress above my fortress, if you know what I mean, a nice castle area as an entrance to my fort, then down below, all the fun stuff begins.