I'm more familiar with the cities on the Capitol Corridor.
Sacramento is pretty walkable. It's on the edge of downtown, there's a shopping center a few blocks away, Old Sac is Adblock away, and there's the Sacramento River.
The various bus stops can be very walkable, like Santa Cruz or all of the San Francisco stops.
San Jose is sort of in a no mans land. There's the arena across the street but it's several blocks to anything that resembles businesses. But a half mile walk and it's downtown. I guess Oakland is, but I'm familiar with the area. It might be different for someone from out of town.
Davis is pretty good. It's a college town and a lot of people get by without a vehicle. Amtrak is a prime means of students to get there and back home.
The Berkeley station is sort of disconnected from the main parts of the city, but the individual neighborhood it's in is very walkable. There's the 4th Street shopping district. There are also some interesting places nearby like Sierra Nevada Brewery's new Torpedo Room that's literally 100 feet from the station. The original SP station building has been converted into a bar and restaurant. Tamara Sake has it's US facility a block away and they have tastings.