Some fun links. On I-5 if you're not prepared to use chains or even carry chains in southern Oregon, then consider jumping off of I-5 in Albany, OR and taking OR-20 to Newport then take 101 south into California - until you can cross back to I-5 south of the mountains.
I like taking 99W out of Portland, OR to McMinnville. Then OR-18 from McMinnville to Lincoln City, then 101 south. OR-18 is a really nice road and drives right past
Spirit Mountain Casino in Grand Ronde. In Lincoln City there is
Chinook Winds Casino.
http://www.oregon.gov/ODOT/COMM/Pages/winterdriving.aspxhttp://www.oregon.gov/ODOT/COMM/Pages/winterdriving.aspx#Chains_and_traction_tireshttp://www.oregon.gov/ODOT/COMM/CRO/pages/answer_team.aspx#chain_and_traction_tire_questionshttp://www.tripcheck.com/Pages/chain-laws.asp As seen on Oregon roads:
http://www.tripcheck.com/Pages/minimum-chain-requirements.asp