I've never fished the others, but I'm familiar with Santa Ana River Lakes and at this time of year, they're
stocking catfish and tilapia. I've never fished for tilapia, but for catfish, I've always used a Carolina rig and any kind of oily/stinky bait from strips of cut mackerel to the Berkley catfish powerbaits. The typical setup is to cast out, let the sinker hit bottom and then reel in until you have tension on the line and then back off to give some slack and then wait.
15lb test is a bit of overkill for So Cal lakes, but it's not a problem in any way. Catfish aren't line shy in my experience.
I've done well at La Palma Corner and the Western side of the North shore point. I suggest going well before opening and getting in line as it can get crowded. WeatherUnderground says the wind won't pick up until the afternoon, so you should be OK to fish any part of the lake, but I prefer a spot where I can set my chair right at the water's edge.
Be safe and have fun!