There is already 2 such widgets loaded on the SGS2 without going to the market. menu, add, widget scroll across a few screen fulls - do you see Analogue dual clock & digital dual clock?
Once they are on the screen hit which ever clock and set as your home location. Then assuming you have your GPS/Network location service running, when you set the other clock - there is a button for current location - hit that. It sets the clock to where you are. Admittedly it's not automatically changed based on your location, but I'd prefer 2 taps to update instead of sucking the battery down polling your location all the time?