Hey! The drive up the coast is lovely, and I've spent a lot of time doing the southern Oregon-Washington drive. Definitely take Coastal Highway 101 instead of I-5 if you want the scenic (but twice as long) route. Steer clear of the tourist towns on the Oregon Coast--- Seaside especially--- since they'll cost more and will be crowded in August. Try for places just outside Cannon Beach, like Arch Cape, or further north, like Astoria. There are a few good campsites there, but you'll probably want to book ahead as they're popular. As far as sleeping on the side of the road, I wouldn't recommend it-- coastal roads are twisty and sometimes narrow, and there aren't great places to pull off. But if you're really short on cash, you can always try sleeping on the beach. You might get caught and asked to leave, but probably not. Arch Cape would be a good place to do this. Bring sleeping bags, build a fire, stay up until the fire burns down, and sleep until morning. Just watch out for high tide-- consider sleeping on the rocks to make sure you don't get washed away.