When you get to the actual train station part and go downstairs to where the tracks are, follow the tunnel on your right (when looking at them from either set of stairs you just went down).
You'll get to a maintenance door about 75 yards down on the right. Go through it, and as you progress, keep an eye out for a sealed door that will be on your left.
* (if you make it all the way to Dr. McCrazy's hideout, then you went too far) *
The "Fire Hose" will be inside this room, along with a few other goodies ...I think I found the "Cherry Bombs" in here too, but I can't say for sure ...I was pretty drunk at this point and almost asleep.
OSFitz posted... I found the key without much trouble, but I cannot find the room "marked with the spinning light." Is this room in the Marigold Station or somewhere else?
* NO Spoilers * ONLY the location *
Yep, I actually just found this last night. If you go past the door that leads to Dr. McCrazy's lab and to the right, there will be a cross over to another set of tracks. Go left and on the right side of the train you should see the room "marked with the spinning light."