I've been sailing in the BVI while the PR Navy came by and they certainly enjoy flocking/rafting together and have a merry time. The marinas get crowded, but the OP was asking about mooring balls; and these will remain relatively free. And not only is the mooring field outside of Leverick big, one can anchor in sand in 20 feet of water just outside of that field.... for free... and spend the money you've saved at the bar.