They may cut it because of the way the plot develops in the movie. In the book, it seems like a lot of time went past with Bella just *thinking* about Edward. But if you really think about it, if the movie had all of those thoughts of Bella's and no action, it'd be boring. So they may just have things move along faster - maybe Bella finds out after Edward saves her from the car accident. Or, maybe it's not an alley scene, maybe Edward follows Bella to Port Angeles and something else happens...they may cut the alley scene itself, but not the part with the men following Bella leading up to the alleyway. Maybe Edward just saves her before that.
Think about it. That whole scene, with Bella preparing herself to fight, was a good number of pages in the book. But on film, it'd take less than a minute for all of that to happen.
Who knows? I think there's going to be a lot of differences between the movie and the book, but I hope they know what they're doing.