Gales Creek, along Hwy 6 headed toward Tillamook. Unless its changed in the last two years since I moved to Texas, its open year round, fly & lure only regs. Start fishing at Dorman's Pond (junction of Hwy 6 and 8) - you can walk down stream to the bridge where 6 crosses it - there's a great hole right under that bridge, and you can wade fish for a long way upstream.
The next place is Gales Creek Campground about 10-15 minutes further west. The campground *gate* closes in the winter, but there's a big wide area you can park without blocking the gate and walk down the road to the campground and access the stream. Fish it downstream or upstream - LOTS of great water to fish.
Creek is loaded with cutthroats. One of the nicest fish I'd taken from the creek in years was 50 feet downstream from the bridge in the campground, Czech nymphing a team of soft hackles & simple caddis patterns.
There's some much deeper holes both down stream and upstream of the campground that is great to run a streamer through. Aggressive takes.
Take lots of water / gatorade and a lunch. Make sure you have good slip resistant wading boots - I'm a big fan of felts still, even though a lot of people are switching to rubber soles. Slipping and falling on your head sucks.
Gales Creek is PERFECT 3 weight water. Your 5 weight will work, but the 3 weight is great for that stream. Its not real huge, you dont' need to make 40-50 foot casts but there are places you CAN make such casts.
Another stream I really liked to fish is the Youngs River above the falls - it was one of the first coastal rivers to open to year round angling. Access it off Hwy 26 near Seaside, its a little bit of a drive in, but last time I was up there was in a compact sedan, you dont' need a truck to get there unless its snowy. Its another small stream that doesn't require long, technical casts or drifts to get into fish. Don't expect monsters up there, but you WILL catch some fish.
IF you can afford the drive - the Deschutes is a great place to exercise your 5 weight. You do NOT need to make huge casts to catch fish. I hooked up with a steelhead on a 20' cast, fishing for trout the last time I fished it. If you can throw a nymph rig, you'll catch fish on the D. If there's bugs on top - so much the better, you can get your dry fly game on. Don't be afraid to fish a streamer either - people say the Deschutes fish are not meat eaters - they dunno what they're talking about, or they're lying to you trying to keep the secret for themselves. Woolly buggers catch a lot of Deschutes fish.
Its another fishery that is open year round, and late season fishing can be epic.
The Metolius is another river with year-round fishing - its also one of the only places you can legally target bull trout. Take a heavier rod for them - 7 or 8 weight, throw big meaty Kelly Galloup streamer patterns. Otherwise - nymph with your 5 weight. The Met is a gorgeous river.
If you make it out east, the Grande Ronde River is another one your 5 weight would be great on. Open year round.
If you really venture east - do yourself a favor and fish the Owyhee River. Take everything - nymphs, dries, streamers. Some nice browns to be found in addition to rainbows.
