My advice to you is this:
As soon as you cross the border, pull over. Put on a holster and wear your sig with pride.
ok, so make sure you know Oregon's laws on firearms too. It is a fairly friendly state for OC. When you are here, CA's firearms laws do not apply to you. There are a few certain cities that ban OC without a CHL. Make sure you know those cities. If you are just driving through the city I believe it is OK to OC in your vehicle (somebody please correct me if I'm wrong). Just don't stop there. There is a list of those cities in another post somewhere in the Oregon forum. http://www.leg.state.or.us/ors/166.html are the Oregon statutes that address firearms.
While you're here, see if you can get a sheriff to give you a CHL. Wouldn't hurt to get it done so you have it when you move.