They are normally found in acidic soils where moist levels are high; usually in well-mulched gardens. They are very active at night which makes it difficult to place the blame of your damaged foliage on them. During the day they sleep under bark, wood, leaf debris, clay flowerpot bases or similar dark places. They become particularly active during rainy seasons or in shady areas. They aren't striclty limited geographically, so chances are you've come in contact with them.
Plants that have been attacked by slugs will have ragged holes or torn edges in their leaves, stems and or fruits. They some times leave behind slimy trials. They are non-selective in their eating habits but hostas are their preference. Just about anything goes!
The best way to get rid of them is to hand pick them if you find them early in the growing season. Another method, which is much easier than touching these slimy buggers, is to place a small paper cup cut in half (about the size of a spray paint can lid) and fill it with 3 ounces of beer. I don't think they are particular, but I used Bud Light last summer and after 3 days of tossing slugs and stale beer then replacing with fresh beer my slugs were gone and never returned. You can buy commercial traps that have covers to prevent the rain from dilluting the beer but the cups will work just fine if the rain is not a factor.