At Spanish Bottom a steep but easy trail goes up to the Doll's House, named for its fascinating rock formations. Spring is excellent for canoeing the Green River. Although April can be chilly, the river will be less crowded. May and June generally have the highest water, and peak in popularity. By June, the days can be beastly hot.
Autumn is reportedly good, but it can be rainy and cold.
This is a completely remote canoeing experience, so be sure to be prepared for extreme conditions of weather. Fortunately most of them are large enough so that several parties can be accommodated without too much disturbance of the wilderness experience. Most campsites will require a scramble up the bank to higher ground, sometimes a few hundred feet from the river. Since these are not always obvious, consultation with current guide books, or your outfitter should help you locate the good camp sites. Within Canyonlands National Park, a back country permit is required for camping on the river.