San Juan is not noted for many trout of size , better off going into Fairy Lake and /or fish the mouth for cuts.
You can take a look around at the other systems there but the flows are pretty strong right now.
Cowichan should be getting into swing now for trout , as for 6w for steelhead , its your line I guess , I have a 6w Hardy that I use for trout and never contemplated using it for steelies , don't think you can run fast enough down the river banks to keep up with them after they have spooled your line on a small fly reel though.
If you try it let me know how you did.
Luck
AL