I love California diving but it doesn't compare to Caymans or Cozumel except under rare circumstances and it is colder and generally more difficult. This winter and spring we may be impacted in a major way by El Nino storms too. Come in Sept-Oct 2016 and dive the Channel Islands and you may love it.
I'm scheduled to come try California Channel Islands in 2016. I've been researching the California dive scene, and when you mentioned it doesn't compare to the Caymans or Cozumel, I agree, but I'd clarify that it's a different kind of diving. From what I understand, on the negative side, California is...
1.) Colder.
2.) Lower viz.
3.) Sea conditions more apt to be rough?
4.) It's not a 'pretty reef' destination with loads of hard corals.
Gee, sounds like crap. Why go? For me, the following were issues:
1.) Haven't been, or dove the Pacific Ocean.
2.) I'd like to dive a kelp forest at least once trip in my life, & kelp only grows in cold water. The unseasonably warm water this year has hurt the kelp badly in places, but it can still be found.
3.) Diving with pinnipeds (seals & sea lions) sounds like a trip, & I've love to. Yeah, you could head farther south than California & do it in warmer water, but California's such a major U.S. dive destination, I'd like to knock if off the bucket list.
4.) Different sea life than I'm used to.
All that said, conditions vary by season & region. It's not like Bonaire or Curacao, where you can go any time, with your only fear that icy conditions will prevent your home flight from leaving to get there! Day boat trips aren't evenly distributed all week, and they may require a minimum # of divers to go. If you're staying on Catalina Island you've got a good shore diving option, & some mainland locations maybe...I'm aiming for a 5 day live-aboard trip, but not bringing non-divers.
Whether California is a good dive destination for you depends on what you've looking for, and what you're open to. It doesn't compare to Cozumel or the Caymans because it's a different kind of diving. If I had to pick what kind of diving I want to do for the rest of my life, it wouldn't be California. But I'd like to try it once!
You could always try
offshore wreck diving with sand tigers sharks out of Morehead, North Carolina, for something different. It's not party central/touristy, but it's coastal mainland U.S.A. & there are things to do.
Richard.