Elaine and I were in the Tri-Cities area of WA this past week, and found the trail system to be great. It could use a few more signs, but it's a good system that allows you to ride alongside the river for many miles (20+), and designates bridges that have separated walkways to accommodate bikes for crossing the river. Their trail map also shows longer routes that utilize the roads around the area. We stopped at Sacagewea State Park's interpretive center for historical exhibits about Lewis & Clark, and also about the history of the area. The Ice House brew pub in Kennewick is worth a stop, as is McGills on the Pasco side.
Don't go through the dirt; even their map warns against the nasty goat head thorns. Also, wind can be a real factor here. All in all, worth a look.
