Travel up HWY 21, winding your way through mountain roads. You'll arrive at the namesake campground for Bonneville Hot Springs. Take a short hike (.25 miles in the summer) to find a hillside soak shack and several pools along the river. The shack houses an old tub, which is in pretty good shape and barely holds two. If you're looking for privacy, that's the place to soak. Down by the river you'll see the silt bottomed user built pools. They vary in temps, but are all usually a fairly nice soak. However, depending on water levels you may have to stir the water to keep the temps even (not my fav, but works nicely).
During summer months these springs are extremely popular. You'll have difficulty getting them to yourselves, and will definetely be sharing the campground. Winter months offer a bit more solitude, however it is a prevalant snowshoe/nordic area. The campground is closed from first snow fall through mid May, which leaves you to park along the highway in designated areas. Swim suits are a definite must, unless using the shack.
My last visit was January of this year. It was the ideal time. The hike was quite enjoyable. With only the sound of our boots crunching the crystalized snow and the wind whispering through the pines, all was quiet. I did pass another couple, he was on snowshoes, she was on skies, both were friendly. I patronized the shack, as the air was very crisp. Despite the popularity of this area, it holds extreme beauty, wild flowers, and the occasional wild life sighting. In the past I've seen deer, elk, and a few families of turkeys. As usual, please step with a light foot and leave as little trace as possible. While the trash levels are normally fairly low, many like to leave their garbage where it doesn't belong. Thank you in advance for taking care of Mother Nature.