Postpaid to prepaid at&t iphones?

So my phone number and my 2 other brothers phones were under my aunts name and now she wants to cancel the plan with at&t! We don't wanna lose our numbers so at&t said to go to prepaid plans (the 3 of us) we couldn't get the numbers under my name on regular plan cuz i don't have any credit history. They said unlimited text & calls and 2GB of internet for $60 which sounds reasonable. Would the internet be fast and good? Is the prepaid plan worth it? Any good experiences and bad experiences! After i get my credit score up ill transfer to postpaid.

I have iphone 5S
2nd bro- Iphone 5
3rd bro- regular phone

Read the small print before you commit as $60.a month for unlimited text & calls and 2GB of internet for 2-smart phones and 1-reg. Phones is cheap