Channel Islands are great take a short live-aboard trip i suggest the Sand Dollar boat or the Pacific Star boat you can google them for more info.
Monterrey is great go to Bamboo Reef Scuba to make a reservation for a guided tour they are great I have had Adam Lester as a guide a few times hes great. Point Loos is a preserve and has great sea-life but you need a reservation to dive there but its easy to sigh up for.
Hope this helps
Norm