From Avalon, you can walk the road South down towards the quarry where I've had good luck too.
This path is closed to pedestrian traffic with a fine of over 200$. You can take a taxi down to buffalo head restaurant and then walk down past the last boat mooring to start spearing. But be warned that GWS have been spotted there numerous times.
Also you can rent a Kayak and go north from descanso beach. There are numerous small kelp beds up there and some good halibut sand as well.