The information kiosk lists the Rainbow Falls trail as 3 miles. It doesn't say, but this is round trip and I'm assuming that is to this viewing area. I timed the hike to this point at about 40 minutes. The hike begins at the kiosk, just follow the orange tags nailed to the trees. In about 5 minutes the trail turns right. Going left is the old trail (road) that just leads back up to a now closed section of Grassy Ridge Rd beyond the parking area. Continue down the trail, cross a small creek and get to the national forest boundary about 20 minutes from the parking lot. In another 5 minutes you arrive at the river. Notice a lesser trail going to the left and down to Stairway Falls. We didn't go there today, but it's 10-15 minutes to the top of the falls. And you'll pass a small campsite.

Turn right to go up to Rainbow - there are no signs - and immediately cross a smaller creek. The trail then comes out a a nice camping area suitable for a couple or 3 small groups. Once this trail catches on, I suspect these sites will get a lot of use. Another 10 minutes up the trail from the camp sites is the swimming hole and small falls. It's fairly obvious where people go down to get out on the flat rock in front of the falls. We didn't stop today as I was mainly interested in taking notes. The trail from here up to Rainbow Falls gets steeper here. Depending on your stamina, you should be up in 5-10 minutes for this fantastic view of the falls. If you get here early on a sunny day, you should see a rainbow at the base of the falls. People swim here as you can see. They also cross over on those rocks and climb up to the ledge to the left of the falls and jump as these people did.