National Weather Service
NDBC - Southwest USA Recent Marine Data
The first link is to the NOAA forcasts and the second is to the Bouys in your area. By reading these and correlating to conditions on the dive site you can, over time, get a feel for what the dive site will be like. Factor in the tides, the direction of the swell, and how long after a storm the viz gets better and you have a better chance at good conditions, or know what alternate site is better to dive.
Dive shops sometimes have site conditions from folks returning gear or refilling tanks.
Also check for "ocean cams" in the area to get your eyes on the ocean from your computer.
It takes time to develop a feel for predicting conditions. And even now, sometimes when I get there I'm wrong so I hope you don't have the hour and a half drive I do to actually see the conditions.
Bob
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There is no problem that can't be solved with a liberal application of sex, tequila, money, duct tape, or high explosives, not necessarily in that order.