I usually look only at the number of clicks and the number of new depositors. How may new depositors do you have with this place?
I like to see ratios of 50:1 (that's 50 clicks per new depositing player), but that doesn't happen very often. Usually my numbers are around 150:1 on average. Some casinos convert better than others. I've had some convert so horribly that the ratio is over 1,000:1.
I'm not sure if this is useful or not since you asked about the downloads and signup ratios.... I don't pay close attention to those figures, so I don't really know.
I'll check some of my accounts and post again later.