For the Stevenson to Home Valley run you will find a rock island about halfway through the run (slightly WA side) and another set of rocks right before the take-out. The safest thing to do is to pass on the OR side of the take-out rocks and then come into Home Valley. It is possible to shoot to the inside of those take-out rocks, but there are more, hard to see rocks on the inside that you may or may not see (depending upon river level).
The Home-Valley to Drano Lake, in my opinion, is more straight forward and easier. Usually, its calmer on the WA side, and you can venture out towards the middle as conditions and your comfort level dictate. No rocks to worry about. Drano Lake can be identified by the train trestle that spans the inlet.
On all legs, watch for barge traffic and gill nets that are marked by large white buoys. Make damn sure that you're leashed well to your boat. The river flows west and the winds blow to the east. If you fall off your boat and you are not leashed, or if the leash fails, you go one way and the boat goes the other. You will be instantly separated from your boat and you will NOT be able to catch it.
Be safe, have fun.
Here's a link to the best forecast site: http://thegorgeismygym.com/forecast/
Here's a link to the best paddle wheeler wash ride you'll ever have: http://www.portlandspirit.com/sternwheeler.php#sightseeing
Good point about leashing up. I've ridden over the gill-nets with no harm to them or me. But my imagination goes nuts when I think about coming off the boat near one.