There are a few different campgrounds in the area. The best bet would be Myrtle Beach State Park that is a campground and has a pier as well. Also, you have Apache Pier and Campground in the North Myrtle Beach area. They're about 20 miles apart. Depends on what you like to catch. Apache has an artificial reef underneath and the State Park is very sandy.
Surf fishing at that time of year, you're likely to catch alot of sting rays and sharks. Do not let anyone see you land a shark. In that county, you can be arrested for it. It's a stupid law, but they enforce it. Spanish mackerel, blues, puppy drum, kings, summer trout, and flounder can be had from the piers and surf during July/August.
My favorite piers there are 2nd. Ave and Garden City. They're good folks, look them up.