Take I-10 out to CA, work your way over to US 101, then take US 101 up the CA and OR coasts (or near to them). Once you're in northwest OR on US 101, you can drop over to Portland area by US 30, US 26, or other roads. Just stay in touch with local radio and ODOT travel info. Getting to US 101 in CA is probably best done by taking I-5 up to the northern part of the state and then take CA 20 over to US 101, however there are many other ways to get over there also. Other respondents will have useful info for you to follow.
