Here's a couple Spectro shots... always a challenging subject.
The lens was the Pentax 50mm F1.4. ISO for both is 1600. The first photo was shot in Aperture Priority, F1.7, 1/500th second. The second was shutter priority, 1/90th second, F1.4, +1.50 exposure compensation (without the EC, you wouldn't catch the details of the costume, just the lights.) Metering was "multi-segment" according to the exif, which I believe means that it was the default entire-frame metering.
I didn't really try many dark ride on-ride photos, but here's a couple from Snow White's Scary Adventures. Pentax 50mm F1.4 again, Program mode (I think the ride stopped so I shot these without preparing), spot metering, ISO 1600. The first is 1/60th at F2.0, the second is 1/125th at F2.0.
Here's one that I kind of like, it's something you rarely see photographed and while the results weren't stellar, I think they're not
too bad. The Space Mountain queue!
This was with my Zenitar 16mm fisheye, which means full manual mode, ISO 1600, shutter of 1/6th of a second (I wish I had the IS of the K100D or K10D), spot metering. The aperture isn't recorded with this lens but I'm assuming that I had it set to the max (F2.8) or very close.
Next trip, I plan to attack some more dark rides with the 50mm F1.4 or perhaps a wider F1.8 lens.