The only campground reachable by road in the park, Castilletes sits on 1.5km of beach that's also the park's most popular spot for sea-turtle nesting. It's handy for its accessibility but can't compete with places further west for atmosphere and all-round service (the tents are laid out in regimented lines very close together).
The beach is swimmable in September and October.
Parking is free, while Cañaveral, the starting point for most of the trails, is 20 minutes away on foot.