No, it won't break your game. I've done this myself to create a blank template when starting a new game. Just one thing you should know if you have the Get Together EP. That pack requires a minimum of ten clubs in the game at all times. So, if you delete all the premade clubs, the game will create ten clubs and fill them with newly created townies.
Unless someone has created a mod for this, there's no way to stop it from happening. What I did for my 'blank' template was keep at least one Sim in each of the premade clubs. Some Sims were in multiple clubs, so at least I didn't have to keep ten premades. Over time, once you've made ten clubs of your own you can then delete all the premade clubs.
Also, you can't stop the game from generating townies for various positions around the worlds and 'extras' it thinks you need. For instance, if your Sim goes to a park, the game will generate a bunch of Sims. If they go to a gym, the game will generate a trainer, the library will generate a librarian, etc. Just an FYI... :)
EDIT: Okay, I just re-read your post and it sounds like you won't mind if the game generates new townies. You just want fresh faces in your new save. I was thinking you wanted a completely empty game, which isn't possible. Opps! You should be fine. :)
