sounds like a nice ride... bike to Sac and back or just bike it there and then Amtrak it back
.Hmm maybe this would / could be a nice group ride thing.
I've done that ride, starting at the Amtrak station in Martinez. From there it is about 85 miles through The Delta to Old Town Sacramento. We each lunch there, and take the train back to Martinez.
Going to Sacramento is a nice, scenic, fun ride. Riding back can be a b!tch, because of the prevailing headwinds. That's why we start at Amtrak - so we can take the train back.