Taking outdoor pics of people when its sunny.

As cameras become more and more automatic, it is harder for thier owners to be 'photographers'. I was trained as a photographer many many years ago on large format, film cameras with no meters and digital was something for the science fiction books. I rarely put any of my digital SLRs in one of the automatic mode.
With your SD600, you have very little control that you can use to overcome this issue. but you DO have some...

First trick is to manually turn your flash on, even in bright sun when shooting outdoors, (this will do two things, turn on the flash which will provide some fill light on the faces of your subjects to reduce the range between the darkest and lightest areas on your people subjects; and it will change the length of time that the shutter stays open to compensate for the slowness of the flash. So you are puttting more light on thier faces and allowing light to pass thru the lens for a longer duration.)

Second, wear a white shirt/blouse. your subjects are in bright sunlight, but the faces are dark - tells me the sun is behind them and in front of you. Thus a white shirt will reflect light and you become a reflector of sorts (this is a short range trick only) Be mindful of the color of your shirts here, color also reflects and may cause their skin tones to become slightly 'off'.

Also try to get your subjects to step into a shady area so that there is not such a high range difference between the brightly lit areas and shadows on them, some cameras, yours included can only do so much -

Look at it this way, I can ask you to someone to swallow a grape in one bite, maybe something the size of a lemon is possible, but you cannot take an entire potatoe into your mouth at one time. In the same way, your camera can only take in a given 'range' of values (intensity) from the darkest to lightest before you exceed it's ability. anything brighter than a given level is simply blown out and anything darker than a given value simply records as black or dark with little or no detail.

This is why a lower pixel count SLR takes better pictures than a high pixel compact camera. Most folks only read the pixel count and go 'ooh ah' - because that is how cameras are marketed. (lots of points recording lower quality range vs fewer points recording higher quality range)

Find ways to stay within the range that your camera can accept. add light to the low end as in tips one and two or reduce the high end, as in tip 3)

Let me know how it works out...