I have not seen that coffee grounds have had any value as a deterent to slugs and what value they might have as a "green" will depend on how much of the nitrogen they do have has evaporated into the atmosphere. Mixing those coffee grounds into the leaves would be better than simply tossing them on top.

i agree, within the safety of a compost pile the grounds can decompose at a much quicker rate, and won't acidify your soil.

OK ~ Thanks guys. I see where it is supposed to be the caffeine that kills the slugs and it must be a very strong dosage of it.
I know it would be best to mix the cg's with the leaves but I'm not digging through 2 feet of snow to get to them. I'll just mix in what's left of them in the spring.