(Did my grad research on thed Lower Columbia)
1st x-USA trip was on US 30 - - bleah!
OR 202 is way nicer - there are sufficient facilities -
Been a while - but the traffic was almost nonexistent after you get out of the Astoria area.
Vernonia is about 60 miles from Astoria and has great camping and bike-oriented facilities.
For my money, WA 4 across the river is the ticket.
It means riding across the Astoria bridge - woo-hoo!
(Or getting a shuttle if you aren't ready for that.)
I like Cape Disappointment way more than Fort Stevens.
The coastline at CD is rugged - at FS it's a sand spit.
Then the ride along the Columbia River is spectacular in places.
I would suggest riding down to Chinook (a bit busy)
Then up to Naselle - then east to Skamokawa and Cathlamet.
There's a back road thru Columbia Wildlife Refuge right on the river.
Skamokawa and Cathlamet are both wonderful Lower Columbia fishing communities -
Beautiful campground on the river at Skamokawa -
Marina at Cathlamet which permits camping on riverbank.
If you are heading east on the L & C - you can stay on the north side -
And skirt the northern suburbs of Vancouver, WA.
WA 4 does get a little busy at 8 and 4 with little shoulder heading into Longview.
Or you can take the Cathlamet ferry - a nice feeling -
And either do US 30 - or climb up OR 47 to Vernonia.
You really can't beat Skamokawa and Cathlamet -
To give the start of your trip a nice feeling.