Well Julia,
In my humble opinion, slugs and snails don't seem too bothered about soil types, you just get a different species of slug/snail that prefers that soil type, I'm close to woodland, so I get slugs like the leopard slug, as well as all the common or garden types.
Some of the gardening expert seem to send out mixed messages, saying things like : Try not to be too tidy, work with nature rather than against it. In the next breath they might say something like : Keep the garden tidy, don't leave things laying around like old pots or plastic sheeting, that might act as a harboring or breeding ground for these munching mollusks.
Other factors to consider, is that some areas may have more things that predate on the sluggs/snails, like song thrush's, hedgehogs, toads and the like.
What I would suggest is try to attract would-be slug eaters and if you have stack of pots etc, then store the in the shed or away from your crops to minimize any damage, I guess its never gonna be all roses in the garden but hey life's for learning, and we gotta keep trying!
Good luck...but give the coffee grounds a try!