iPhone and Home Wireless Network - iPhone newbie

[dd4au]

I recently added an iPhone 4s to a personal Verizon account.  My business account has unlimited data and text, paid by my company.  I use a Blackberry Torch there, but my question involves the personal plan.  I've got a 2 gig data plan for my wife and son.  My son has the iPhone 4S.  Should I set it up so that it accesses our wireless home network when here at home?  Would that save any data useage by not accessing the internet or apps over the Verizon network?