Just got back tonight from hunting the past two days on Assateague Island. Saw widgeon, tons of black ducks and buffles, hoodies, gadwall, couple mallards and some red breasted mergansers. Ended up limiting out on black ducks both days, hen widgeon this morning and shot some buffles. Good amount of ducks on the island but mostly loaded up with black ducks and buffles as usual for Assateague. Not sure where your planning on going in the OC area, but if you're going to Assateague your mallard deeks will work just fine, the black ducks will work into mallard deeks. Although if you can get your hands on some black duck decoys and mix your mallard deeks in with them it seems to, at least in my experience of hunting there over the past ten years, to greatly increase your odds. I've never hunted anywhere else besides Assateague in the OC area but the marshes seem to hold all varieties of puddlers, and the bigger water like the bays have divers(buffles, scaup, mergansers, ring-necks,again my experience) and brant. Hope this can help you out some or at least help to provide a little bit of insight from what my experiences have been over the years. Good luck and happy hunting.
"If you're too busy to duck hunt or catch fish...you're too busy" -Jase Robertson
"Well those ducks flared nicely" -Me