Is Myrtle Beach Travel park overly crowded in the summer months?
Yes but unlike a lot of campgrounds no one seems to get out of control and Security keeps a handle on things. My recommendation is to go after mid-August if you can. It quiets down as a lot of schools are already back in session.
Looks like the "gate" question wasn't answered. Yes, the gate is locked at midnight. However, there is a parking lot right outside the gate. You can park there and walk in. If you need to get out in an emergency when the gate is locked it does trigger from the inside of the campground.