Newb question on buying a Touch for Sprint

[NinjaKnight]

Hey guys, I've got a little question. I've been reading up on the HTC Touch, and it seems like a really great phone. I'm thinking of getting one for my girlfriend, who is on a family plan with Sprint, so she doesn't have any data or anything.

I was wondering if I purchased a Touch locked to Sprint, could she just put her sim card in and just start using the phone on the family share plan? I've heard that you need to buy a data plan, so I'm hesitant about doing this.

Thanks for any help, I really appreciate it.