Hi there

Rockley Beach has sort of lost its attraction to me, my recommendation would be Carlisle Bay for sure.

The approximate taxi rate (car - up to 4 people)
Rockley Beach - US $ 30.00 round trip
Carlisle Bay - US $ 24.00 round trip

You can walk to Carlisle Bay as it is about 15 minutes walk from the pier or you can catch the Bridgetown Shuttle (organised within the port) for US $ 2.00 p/person (each way) and then walk for 5 minutes from the drop-off point.

The attractions...Why Carlisle Bay???
1. Numerous beach bars/restaurants (Boatyard / Copa Beach Bar / Lobster Alive / Harbour Lights etc.) located on a one mile stretch of white powdery sand. All locations offer umbrella/chair rentals and most are party oriented.
2. Superior swimming with many water sports options including snorkelling of ship wrecks.
3. Walking distance from Bridgetown, should you want to do a little shopping.
4. 8 minutes drive by taxi (in either direction) verses 20 minutes from Rockley Beach.
5. PERFECT beach for people watching as this is the busiest beach on our island in Cruise season...very similar to Orient, for unfortunately no naturalist opportunities.

Though Rockley has some interesting points, none weigh as well as Carlisle Bay.

Hope this is helpful...