Don't do it.
The only diving spots north of San Francisco are on the Sonoma and Mendocino coasts, aka the "North Coast."
The sites are rugged. There are zero services (save for a few spots way up on the Mendo coast, but Monterey would be closer). You're a good 1/2 hour drive from the nearest cell coverage. The ocean there is unforgiving. Some days are divable. Some aren't. Even in best of times, it's cold (44 to 52F) and low vis (3-12 ft.).
No way I would advice someone to do their first cold water diving there without an experienced, local instructor.
I dive there a lot and am active in the North Coast Divers.
www.northcoastdivers.org. I love the place, but it's not for unaccompanied newbies to that environment.
MUCH better to drive down the Monterey and hire a dive guide. Any of the dive shops there can set you up right. You'll have a great time, both in and out of the water. Plus, you'll survive the experience.
Here's a link for great information for divers visiting Monterey. http://www.garlic.com/~triblet/ba_diving/newmontereydiver.html
Have a great time.
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