I climbed at Moody Bay and Tiger Bay one day this spring. Both of these had a wide variety of fun routes. The location was surreal as I had never climbed on a beach before, let alone one in Vietnam.
We rented gear and got transportation to the crag from Asia Outdoors. The gear was good as was the boat trip. We did not hire a guide. I think Asia Outdoors could probably help you find someone to climb with.
The whole experience was really interesting - you take a large boat out near the location where you are going to climb, then get on a small boat that takes you to the crag. The small boat hangs out all day and if you want to climb a route that starts over the water rather than on the beach you start from the small boat.
Just don't expect that the boat driver will speak English or know anything about climbing. And when the clock hits whatever time he was told to leave he will be ready to go whether you are on the ground or mid route. He's not going to leave without you but it took some back and forth to explain that, no, we can't just hop right back in the boat, someone is up on the wall. Bring a watch and be ready to go back for lunch or leave for the day at the appointed time.