Sorry shane, I just noticed you'd asked about the beach at Jomtien. I'm not the best person to ask about such things as I don't generally swim at the beach (I prefer the pool - no skin irritation from the pool!!)
But plenty of people swim at Jomtien (also at Pattaya).

Tintin mentions some things which are in Pattaya, not Jomtien (Walking Street is in Pattaya and also the particular music venues that he mentions)