At the same time, I also purchased the larger Canon "S2 IS" with the 12x zoom, thinking I would get greater depth of field control...(didn't do my research that well...) (The a420 was bought later, as the S2 IS was too large...) Would the aperture rules on this camera be the same as the A420??
yes, the same rules apply to the S2 IS as well. As far as focusing on the background and makiing the foreground blurry, I'm not sure why you would want to do this, seems backwards to what everyone else would want, but to each his own. It will be difficult just as it is difficult to blur the background, maybe even more so. Your forground subject would have to be fairly close to the camera and the background far away. So if you wanted say a person or something of similar size in the forground to be blurry and be completely in the frame, that is going to take some experimenting, may be hard to get something of any size in the forground to be blurry. You may have to resort to post processing to get the effect you want.