Amtrak from Portland or Seattle to Eugene is very easy
If flying into Eugene is expensive or inconvenient it is easy to take Amtrak to Eugene from Portland or Seattle. They have bike hooks on the train so it is not necessary to disassemble your bike in any way. Taking Amtrak south from Eugene is not as much fun as the train trip becomes ridiculously long. When taking Amtrak bring your meals and snacks with you. The food on the train is similar to what you will find in a vending machine.
As noted above the ride from San Francisco to San Luis Obispo through Big Sur is beautiful. I just rode the section from Carmel to San Luis Obispo in April when the road reopened after slide damage and then took Amtrak back to Carmel.