Re: Fishing from the surf in Myrtle Beach.
I've spend some time fishing around Pawley's Island, just south of Murrells Inlet.
Haven't spent enough time there to have done to well with flies yet, so when I get down there I take other tackle too. Take some basic stuff, Deceivers, bucktails, Seaducers, Clousers, Half & Half's, plus perhaps some topwaters like poppers & gurglers. These will all work on various species. Take some small crab & shrimp patterns too, primarily for the Redfish if you can find them in shallow water. Various colors, olive, tans, browns, pearl/white, pink. Sizes ranging from 2 to 2/0 & about 3 to 6 inches long on the various streamers, and size 4 to 1 on the crab & shrimp patterns. You don't need to have exact imitations. It can be much like fishing for bass, most salt species will eat whatever you can get in front of them without spooking them, except salt species move around a lot more.
You'll have to fish the tides too. Unlike bass fishing, unless you're accustomed to fishing in tidal waters, tides will influence when & where the fish will be. Sometimes a specific phase of the tide, either out going or incoming will be best. It usually depends on where you are.
While you're there, you may want to check out Huntington State Park, which is between Murrells & Pawley's. I have not been in there, but from what I've read there are creeks & back waters you might find are conducive to fly fishing.
Hope this helps!