Here's the Oregon 2008 Traffic Flow Map -
It might help you decide based on traffic levels.
http://www.oregon.gov/ODOT/TD/TDATA/...p_GIS_2008.pdf
The stretch of US 101 south of Cape Blanco is one of the nicest rides out there.
But getting inland is - as you say - a tough choice.
US 199 from Crescent City is pretty busy with so-so shoulders.
People bike it all the time.
Plus there is the tunnel.
Long, narrow, no shoulders. Moderate+ traffic.
Does have flashing lights.