I have never had any trouble leaving my backpack on my chair, with a towel and going in the water at Sunbeach, Bourbon Beach, Cosmos, BarBBarn, Roots Bamboo, or anywhere along that beach. I dont stay right on the beach either, and take a backpack with some cash (not alot) my camera, water, book.. you know stuff, and nothing has ever gone missing. Maybe i'm just lucky or something though.

I wouldnt let the idea of the 'higglers' on the beach bother you. You will be approached to buy things, but a polite and simple No Thanks works best for me.

Hmm.. your best bet is taking a Route Taxi from the WestEnd to the Beach.
It will cost you 100J (80J i think but i dont play with change so i give a 100J -- unless its changed since March) to go from your hotel on the Cliffs, to town, and then another 100J to anywhere from town down the Beach Road... per person.
Sometimes you will have to change taxies in town, but most often the driver that picks you up will drop you off where you want to go. Just remember that each leg of the road is paid separately.

Have fun Sunbrnd!