Green river is a good choice. Launch at Flaming Geyser or Fuller bridge. Easy float with limited experience . Nice scenery. I have not been on the river for a while due to health problems so input from others would be a help. After gaining experience the upper river is a real fun float with some class 4-5 rapids.. Most of a day from Palmer to hwy 18. with stop for lunch and fishing on the way. The upper river has very little access so once you start you are committed to the river, Have fun