If your friend wants a really pretty place to drop a line in, then don't overlook our local mountain lakes. If he has mobility issues and really wants to catch his dinner, then Santa Ana River Lakes is by far the best place to go. If that is the choice, then remember that SARL is completely man-made, they brought in CAT D-9 bulldozers and scooped out the ground to make the lakes. Think "bathtub" and you will be right on the money. No long sloping gradual depth, but a bank going into just a few feet of shelf and then a very sharp drop-off.
Remember also that these are all stocked trout, even the nice fat big ones. They spent their whole lives in bathtub-shaped pools, mostly swimming around and around the sides. So the fish are NOT out in the middle of the lakes. They are going to be found very near to the sides, not far at all from the shore, because that is where they have found the food all of their lives.
The SARL lakes are closed on Thursdays so that the fish can be stocked and become a bit acclimatized to the new water. So Friday is a good day to go, or Saturday if that is the earliest he can get away.