Vin,
June is starting the cold season for diving in the Monterey Bay Area. Believe it or not, the diving here is "better" in the winter when the water is warmer and clearer.
That said, there is still real good diving to be found, but I would focus on Monterey and Carmel. I am sure that there are some good diving spots in SF, but I don't know of any. Monterey has a number of great spots with shore diving and boat diving available.
There are a bunch of boats in the Monterey Area. Arguably the two most popular are the Monterey Express and the Cypress Sea.
http://www.montereyexpress.com/
http://www.cypresscharters.com/
There are others and there are links to others (Escapade etc) but those listed above are the ones that I know of personally. They tend to run about $80 for a 2-tank dive. (Please remember that I am speaking in generalities!)
--------------------
There are a number of nice shore dive locations in and around Monterey Bay Area. The most popular is Breakwater. If you want to find lots of divers go there. If you want solitude, don't go there. McAbee and Lover's are two others that immediately come to mind in Monterey.
A little south of Monterey is a State Park called Pt Lobos. I think that it is one of the best hiking places in the entire area with fabulous views, seals, otters, windswept rocks and trees, tidepools, cliffs, ledges, everything you could want. They also have some great diving at Whaler's Cove. You need to make reservations in advance to dive there, and you can't dive alone. I don't know the details, but there should be threads that explain it better than I can. I believe that it is relatively easy to get midweek reservations, but weekends sell out way in advance. Here is a link to the state park.
http://pt-lobos.parks.state.ca.us/index.html
Another famous dive site is Monastery Beach, just North of Pt Lobos. There is some real good diving there, but the place is infamous for hammering inexperienced divers when they try to exit through the surf. The "Monastery Crawl" is pretty much required to survive. You never dive Monastery when the conditions are bad, and you should dive with experienced people that have been there before. Monastery is probably home to more local dive horror stories than any other place. However, it is still a popular destination, so that tells you something about how good the diving is.
Search the web a bit, and search the ScubaBoard Archive a bit and then when you know what else you want to know, you can ask us again. There are a number of very skilled, and very knowledgeable locals that will help and that sometimes jump at the chance to buddy with a visitor. They will just want to know more about you and your training and your desires and what you are looking for.
----------------
There are a number of dive shops in the Monterey Area, and those can also be good sources for suggestions. Here are a million CA dive shops:
http://www.scubanaked.com/diveshops.html
Here is a popular Monterey Dive Shop right across from Breakwater
http://www.montereyscubadiving.com/index.html
I could give you a ton more, but my boss just walked in
W