I would not waste my upgrade on a 4S. So you have a few options...
Buy another phone (you can get great Android phones online brand new for really cheap)
Buy a iPhone 4 online
If you must have the 4S, buy it off contract, keep it in a case at all times with a screen protector, and then sell it online right around September 10th-15th for roughly 80% of what you bought it for
Buy another phone (you can get great Android phones online brand new for really cheap)
Buy a iPhone 4 online
If you must have the 4S, buy it off contract, keep it in a case at all times with a screen protector, and then sell it online right around September 10th-15th for roughly 80% of what you bought it for