Last we heard Sprint was prepping to launch its LTE network in 100 cities in the "coming months." Well, a tipster just sent along a some info that seems to indicate that Chicago and Boston will be online before September is out. According to the leaked memo, towers in the areas surrounding those cities should start lighting up soon, with both metropolitan centers set to become "discoverable" on September 21st. Now, that doesn't mean LTE will officially launch in those cities on that Friday, merely that 4G capable devices may start picking up the signals. From that day forward Sprint will be in pre-launch mode in Boston and Chicago, as they build out infrastructure to support the shift to a new wireless platform.