Thanks to Joseph Turner:
"It was taken Christmastime, 1976, in front of the Prospect Ward building. The picture was taken by an Elder standing in the middle of the road - and cars were having to dodge him. If you zoom in, you can see that everybody thought it was pretty funny.
President and Sister Swan are in the center - Sister Swan is wearing red. This picture was taken just after The Mormon Madrigals had finished their road-trip and had performed for the Mission just before the picture was taken. The Mormon Madrigals was a singing group made up of regular, full-time Elder and Sister missionaries. You can see several of them in the group wearing light-green shirts or dresses. I am the tall green shirt just under the "n" in the word "Saints." Elder Kim Hendricksen, my companion, is to my left, and has his head turned toward Sister Swan - he too is laughing pretty hard."