I lived in the LA/OC area for almost my entire life and found out several ways to ride. There are many options and not all are great, but here's what I know:
If it's just you riding and you can't (or don't want to) depend on other people, there is Carlsbad Lagoon (a wakeboard school-www.carslbadlagoon.com) in San Diego county (probably your most convenient option). You would pay a premium to ride but it's only about a 50 minute drive from Irvine. It is a well run service (that I think is open year round). It saves you the hassle of pulling a boat and taking it to one of the very crowded local lakes (and even the lagoon gets crowded in the summer i think). To be honest, it is probably your best overall (though not as cost effective) way to ride if you have a good job. I think if you get a permit you can drop your own boat in the lagoon but it's salt water, and from what I have experienced, salt eats boats no matter how much you flush the engine or take care of it.
Big Bear Lake has a two tower cable (Designated Wakesports) but I don't know if it's still running. Only runs in the summer and is about an hour 45 minute drive. However, it is a lot of fun (I ride mostly cable in norcal now).
Socal Wakeboard Instruction is a school at Canyon Lake but I have messaged them and not gotten responses back so they may not be operational at this time. Worth a call and email though as canyon lake has great conditions and is only about an hour drive from Irvine.
Long Beach Marine stadium is only good on the week days during the summer and during the winter (one of my best days riding was there in January and it was sunny and 70 degrees) but still-it's salt water. Otherwise, during the summer it is completely overrun with people. However, it is probably the closest place for you to ride at about 25 minutes away from Irvine (be sure to bring money for the launch ramp fee).
I honestly wouldn't bother with the local LA area lakes (Piru, Pyramid, Silverwood). Again crowded during the summer and farther away. If you really want to drop your own boat and ride during the summer, your best bet is renting a place or camping site in Blythe, CA on the Colorado River (prob best to do in spring or fall as it is hotter than blazes in summer). A great place is McIntyre campground and RV park (Blythe has great conditions but watch for boat traffic and shallow sand bars).
Also san diego has a club that rides year round I think:
http://convairwaterski.com/bay.html. A bit farther, but it is another option.
All in all, if you are a weekend warrior, your best bet for good water on the weekend is to put on a wetsuit or drysuit and ride regularly in the spring, fall and winter. If you need to ride in the summer on the weekends, head toward the colorado river. Its about a 3 hour 20 minute drive to blythe with no traffic.
If all else fails, you can catch a cheap flight from orange county or LA to sacramento. both of the big cables here in norcal are super close to the airport and you could make a day of it. again come in spring or fall if you need to come on a weekend (as it gets crowded in the summer). you could make a weekend out of it (I tend to go to wake island as it has more beginner features). Be sure to rent a slider board as features will destroy any good boat board even if it's just one day.
Whew! That was a lot haha. Hope this helps!