You've gotten great advice.
I think your best bet will be the No. Branch of the Yuba. Here’s a site with a link to recent reports. Putah Creek looks like it’s blown out by high flows.
Fish First! Northern California Fly Fishing
In addition to the standards (Royal Wulffs or Trudes, Adams., Light Cahill, Blue Wing Olives, Elk hair Caddis etc, or new equivalents to imitate mayflies and caddis like sparkle duns, X caddis, pick up some stuff at a local shop to get up to date info and maybe some tips on access and techniques. You may want to pick up some dry fly flotant also if you don't have any (I like the paste type (DAB, Gink etc) and get some local patterns. You may want some of these too:
Golden stonefly nymphs and dries
Yellow Stimulators 12 -14
Emergent Sparkle Pupa (green and/or orange 14 with or without beadhead) size 14
Beadhead Woolly Bugger (black) size 8, and/or black Marabou muddler size 6.
Some easy to fish and good searching flies, and they’re hard to fish “wrong”:
Emergent Caddis Sparkle Pupa green and/or orange size 14 with or without beadhead- cast across and let swing below you. Let it hang in the current abit before you pick up and recast.
Black Bead head woolly bugger #8 or black weighted marabou muddler #6 - fish on a sinktip with a short leader if you have one, or a floater with a long leader if you don’t. Good for fishing deeper holes, and may scare up a good brown or two.
Grasshoppers, Stimis and Golden Stone dries- good to cast along banks, and are pretty forgiving when it comes to drag, since the naturals often make a commotion on the surface anyway. Stimis and stones are also good for riffles, and they all float like corks and are easy to see. They’re big happy meals, and will often move fish to them, which helps if you casting is a bit off.
Look for current seams, current breaks around rocks, undercut banks on the outside of bends, and top and tail out of pools and other holding water. Seams and eddys where small tribs flow into the streams are also often good. If the river is really roaring, fish are apt to be out of the main current, often along the bank or the first dropoff within 3’ of it. As others have said, mending will be key.
Fly Fishing, Fly Presentation, Mending - MidCurrent
Remember the longer the cast = more line on the water = harder to get a drag free drift. Better to position yourself for shorter casts, the less fly line on the water the better. Fish near stuff first and cast out further to reach out to different angles. Keep moving positions to get good angles. If you’re in water up to your knees in fast water, you’re probably standing where you should be fishing…
A good place to start with a nymph/ indicator is to set the indicator up 1.5x the depth of the water, and adjust from there. You should feel it ticking along the bottom Nymphing can be tough at first. Try short lining golden stone nymphs in riffles and pocket water. You can also try dries like yellow stimulators in the same spots, also with a short line (you should be getting yellow sallies coming off in the afternoon) .
You can also hang a small bead head nymph from the bend of a Stimi or Grasshopper (hopper copper dropper) and use the dry as an indicator. Keep the dropper short 6” to 1 1/2’ max to avoid tangles.
Good luck, looking forward to the hero shots of you and Mr. and Ms. Trout.