Portland - This is where I live, and it's the other half of the Oregon vs Washington struggle I was describing above. Their public transit is pretty solid actually. It's geographically smaller than a lot of other cities so their rail system covers a lot more ground and even goes out into some suburbs.
Seattle - It's getting there definitely, but generally I wouldn't call it a city that's friendly to pedestrians or transit users.
San Francisco - Probably the next best transit city after NYC, but the tech is super outdated (I think the trains are still from the 70s). I visited without a car and used the rail system maybe once. Maybe I did SF wrong, but pretty much every place I tried to go had to be accessed via bus and there were a few spots where I had no other choice but to get a cab.
In general you'll find that the central downtown of a given American city has decent to good public transit and the further out you go the less reliable options, and for most cities you really don't have to go that far to be stranded without a car. This is true for Seattle, Portland, and San Francisco. You can visit them and stay in a central radius without a car, but if you want to go outside that main hub it's not possible. It's also very challenging to commute to and from work via public transportation (again with the exception of NYC and maybe SF).
The head scratcher with these three cities in general is that there is not a high speed rail that connects them. They are all cities in fairly close proximity and there is already quite a bit of business exchanged between them (and a lot of transplants moving back and forth between the three). You could build a rail along the Pacific Coast Highway (which is worn down and needs to be renovated anyway) and have a transit system that also connects LA, San Diego, and touches the Canadian and Mexican borders. Since the I5 is a robust highway that is much more commonly used than the PCH, a giant reconstruction project that includes a rail component could be done with very little disruption to the interstate travel that already happens in this region.