Yes, from what I understand, the 5DII in Av mode with auto ISO, will use 1/focal length as your slowest shutter speed and adjust ISO up (max 3200) to obtain proper exposure.
Perfect. That's exactly what I wanted to know. I only wish that I could do something like "shutter speed compensation" in which the shutter speed would be 1/(focal lengthx2).
I'll have a play with it tomorrow night. I'd be curious to see how IS affects the shutter speed as well.
Thanks for the replies!