Used to be the forth floor on the East side of the Vagabond Motel which is right across the street from the "I" Street U.P.(was the old SP Main and the original Sacramento S.P. Shops were on the same property. All gone now except for a couple the museum will save. The old depot is still there.) main in Sacramento,Ca. It catches anything entering or leaving and crossing the "I" Street Bridge. The trains have to go by slow due to crossing the bridge. The traffic is freight and passenger. Rail fans shouldn't mind the noise but there is also traffic noise as well as the street across from the parking lot is the artery to North and South bound Highway 5 and Highway 5 is elevated above the garage to the west and you will know when any car or truck crosses the expansion joint on the elevated highway. You'll get used to it.
Cross the street to the West, go through the garage, down the steps,cross the next street and you will trip over the California State Railroad Museum.
If you are hurting for a snack, there is a Denny's next to the motel or Old Town Sacramento and its many restaurants are within blocks of the Museum. Be prepared to lay down a few bucks in some of those. The prime rib place across the street from the museum has good food but is a little pricey as I remember.