I think California is too darn big with so much coastline that it would be really hard to get everybody together in one spot. Back when I was doing the famous North Coast Party up in Sonoma County I was getting a few people from the LA area (which became life long friends BTW) and I even got a few once from Alabama, but mostly locals.
One of the guys that came up from LA got so inspired that he started his own called the Socal Party. He had it once in Malibu and also at Leo Carillo. Unfortunately I was unable to go both times.
So I guess my point is there might have to be 2 MAGs, one northern and one southern. The best dive spots should be picked for both. I think most Southern Californians seems to always be short on time and don't like to venture north too far. Monterey would be way to far for most of them and I think the central coast around SLO to Santa Maria is kind of no mans land. I've never heard anyone rave about how great the diving is. I used to live in Shell beach and all I remeber was lots of shallow dirty water. I think that would kind of be a wet towel for the sake of just trying to make it convenient for everyone to get there.
I would pick somewhere great in Socal and pick Monterey for the Norcal. In Monterey you have a multitude of dive shops, charter boats, great shore diving, great restaurants, lodgings, camping? I'm not sure about that, but I think there's some, other top side attractions for the non divers that may be along for the ride.
I just don't see anything better than Monterey for the northern MAG.
The North Coast, hmmmm, maybe but I don't think so. Way too wild, not many sevices, no charter boats but excellent camping facilities; the best in the state, abalone cookouts, campfires, beautiful forests and scenery, fantastic and pristine diving. But it would be a brutal undertaking trying to get everyone prepared for something like that. Besides it's waaaay too isolated and too far north for most people. I think some people that are used to big city life and having everything around them might feel a little anxiety being in a place like the North Coast.
Vote Early, Vote often"
