Yup, ISO 400 is the norm for Dianas and Holgas. Shutter speeds in unaltered Holgas are roughly 1/100. Shutter speeds in Dianas can go anywhere from 1/60 to 1/200, depending on the camera. They're unpredictable at best, which of course, is part of the charm.
Lots of Diana and Holga info and images at www.digitalsucks.com. (Hey, don't look at me -- I didn't pick the name!)