This is actually a great spring. However, this time of year you'll have to park at the trail head and snow shoe in. The campground is closed. We went up in the area a couple weeks ago and there was snow up to our eyeballs in some spots. We hadn't anticipated all of the snow (shame on us) and had left the shoes at home. It's not a bad hike even through the snow. I'd just make sure you bring boot! Another good one (really depends on river level though) and easy access is Pine Flats. It's a campground on the Banks/Lowman Highway. Fairly easy walk/hike, less than a mile from the camp ground pull in. There's also Kirkham by Lowman, which is on your way to Bonneville. To get to Pine Flats from Boise, take HWY 55 up to Banks Lowman Hwy, I believe it is either hwy 15 or 17, I get them confused. Turn up that and go about 20 min and look for the little sign for PF. To get to Kirkham just continue up Banks/Lowman to HWY 21, take a left and you're almost there. Bonneville is just a ways down from there.
Happy soaking!