We are planning on flying into Portland, Or. renting a car and driving down 101 to Redwoods, probably as far as Eureka, Ca. We have a week. Is this feasible? Would State 5 be better coming back to Portland or back up 101? Any car rental problems in Portland? Also, would the end of August or week after Labor Day be best. Sept sounds good - less crowds but will it be damp and rainy then?

I am assuming when you say a week, you mean 7 days.
I would attack the trip as follows.
First drive south from Portland to Crater Lake for a look around. Then continue on to Grants Pass Oregon.
From there go over toward Crescent City. That will put you in some of the Redwoods. Take a whole day to drive down as far as the Humbold Redwoods State Park, which has some lovely groves. Then retrace your steps, staying to the coast. My reason for suggesting this way is that it keeps the sun to your back as your drive north along the Oregon Coast. You may find that this is too little for 7 days of travel. It depends on how much you want to do each day and how long you spend in the groves.

An alternative would be to continue south from Crater Lake to Mt. Lassen National Park via Mt. Shasta. Then you could cut over to the coast. The problem is that there is absolutely no quick way to drive east and west in that part of California. Cal 36 is awful; I know from experience. At times I thought I was driving on somebody's narrow driveway and threading my way between trees. Route 299 is a little better.
As you come north along the Oregon Coast there is a lot to see and do. My favorite areas are north of Brandon and the area between Reedsport and Lincoln City. There is a motel in Yachats that sits right out on a lava spit within a few yards of the Pacific. The surf sings you to sleep. It is fascinating to watch as the waves pound that rocky outpost.

The weather in early September should be good. We were there as late as Labor Day and had beautiful sunshine the whole time. That time of year is normally still the dry season.

While in Portland be sure to go to the park on the mountain side to the west of downtown and take a look at the Rose Test Gardens. These are world class roses by any measure. Also, the Japanese Garden in the same area is nice. But the roses are special.
I believe the general area is called Washington Park. Hopefully another poster can verify this statement.
But just ask where the roses are and I am sure a local person can direct you to the spot.

Bob is right, it is called Washington Park, and the roses are fabulous. There's also a very nice zoo there. One thing you shouldn't miss in the Portland area is the drive on the scenic highway along the Columbia River Gorge, where the scenery is spectacular. As you head East, stop in at the Women's Club Federated State Park (I think that's the name) for an incredible view at the first overlook of the gorge - it's a surprise and quite a treat, as it's the first viewpoint you come to. There are several lovely waterfalls along the way, and the last one you come to is Multnomah Falls, which is the third highest waterfall in North America. There's a hiking trail there, you can go up a short way to the bridge that spans the lower part of the waterfall, or go farther if you like. There's a nice restaurant in a log building at the base of the falls where you can have lunch (I don't remember whether they serve dinner). When you come to the end of the scenic highway (Which was an engineering marvel when it was built), you can go a little farther on to Bonnieville dam, where you can take a tour of the dam, and see the fish ladders and power generating plant. If I recall correctly (it's been ten years since we lived in Portland), the scenic highway drive took about two hours, with stops for the views and waterfalls. You can get on I84, which parallels the river, and zip back to Portland pretty quickly. If you'd like to stop for a swim on the way back, stop at Rooster Rock State Park, which has a nice swimming beach on the river with changing rooms and lifeguards. It's a beautiful place to swim, shallow for a fair ways, and it's fun to watch the daredevil windsurfers who flock to the river here.

In my opinion 7 days is far to short a time period to drive from Portland over to the coast then all the way down 101 to Eureka then back up I-5 to Portland. Why not limit how far you are going? Unless you are the type who just loves to drive and wants to spend your vacation seeing the sights through a windshield then I suggest you cut the driving time down to half and say go as far south as Reedsport or Florence and then back up to Portland via I-5. As for time of year, to us September is far nicer on the coast as all the kids are back in school so far less people and families and prices on motels are lower too. Weather is still good then.

The weather in the Northwest is very changeable, for instance it's raining now. The better possibility for good weather is BEFORE Labor Day, then get the heck out of Dodge before the three-day weekend. Eureka is a coastal oil town with a brown haze and bad smell with Hwy. 101 right thru the middle of it. Whereas, I don't think that I have ever been to Yreka. They tend to be confused because they are often pronounced the same. FYI -- you can do Portland to S.F. (or back) in about 10 hours on I5, so you are never too far away as long as you can get back to I5. Bob's stuff sounds pretty good. With a full seven days you can visit Frisco or Tahoe, if you don't dawdle too much on hwy. 1.

Thanks for the suggestions - they have been really helpful to get a feel of what we want to do. Special thanks to Bob for taking so much time to help.

D.B.---FRISCO???? Please!