In high summer, the beach at Polis campsite gets very crowded, but as you say, you can walk further along the beach towards Latchi to find space.
The crowds are nothing compared to the thousands of people you find on popular beaches like Nissi beach in Ayia Napa however.
Polis campsite only has a few hundred people there in the summer so I guess it's quiet by comparison!
I personally prefer going a bit further down the coast to Argaka to find a completely deserted bit of beach - the surface is the same - shingle and sand, just no other people.
But the campsite beach is easy to get to from your tent!
