My first thought is to fly down, rent a
truck, fill it up, and drive back to Washington. My father thinks it
would be overall cheaper to rent the truck in in Washington, drive it
down, and drive it back.
Sometimes U-Haul, Ryder, etc. have a shortage in one part of the country and a surplus in
another part, in which case a one-way rental the "favored" way may be cheap, and
the one-way rental the "other" way expensive.
It will almost certainly be cheaper to do a one way move. Those big trucks don't get
40 miles to the gallon :-). Get a diesel if you possibly can.
Plane ticket wise, since you mention central California, there used to be really super
cheap plane tickets to Reno from Seattle and Vancouver (gambling trips) if that counts as
Obviously I made the similar move in the 1990's in case you haven't figured it out