IPhone 4s texting: Messages?

My mom is planning on getting me an iPhone but she had already established that she will not buy the texting plan.
And on an iPhone, that green app: Messages is supported in the iPhone…

If I don't buy the texting plan… Can I still send text msgs on it?
Because on my itouch, I use the Message to text people…

The messaging app is free to any idevice like the ipad to iphones to ipod touches. You can still send texts from the messages instead of imessages to idevices, but there will be charges for each text you send and receive without the texting plan.
you could always download a texting app from the app store, all it will use is your data and will not put any charges to your phone.