Having been a recent 20 year resident of the grand strand with parents that still live in the area, I can honestly say there is no real good craft beer spot in Myrtle Beach. Liberty is a typical tap house with about five house brands in rotation with mediocre food. Mellow mushrooms are the same way, lousy pie with 20 drafts of craft and the usual BMC offerings in bottles. The PW in market commons probably has the best craft selection in the area but most of what you'll find there is what you'll find pretty much everywhere. With only three taps at their growler station, good luck on anything interesting on draft. Call before you go.
Owens discount beverage on 82nd has a dusty rack of bottles that somebody from schaffer distributing convinced them was once craft beer. The beer side of Greens Discount Beverage occasionally gets a rare bomber or two (Founders bolt cutter, Allagash Hugh Malone, etc.) but again, selection is wanting. The old Pavilion discount beverage is likewise equipped, but at least has a shelf dedicated to regional brewing like New South, Duck Rabbit, Highlands and Westbrook.
I'll be honest, i've only tried two beers by New South (their pale ale and IPA) and both sucked. Westbrook produces a little better quality but it's still not as good as i'd like to taste. Their White Thai is about the best thing i've had by them and even that gets a B- in my book. They shoulda stuck to contract brewing for Stillwater.
Anyway, look forward to leaving your craft beer exploration skills on vacation when visiting the grand strand. You'll find it's mostly a BMC wasteland, so pack in some suds if you're driving in. If you're flying in, oh well....