Starting 3/9/14 AT&T will be offering a new plan that is pretty cost-effective for 1 and 2 line folks. Basically you get 1 Line, 2GB of Data, Unlimited Talk & Text, 50 GB Cloud Storage, and Unlimited International Messaging for $65. If you add a second line you get that 2nd line for $25 bucks more. You are going to want to take the plan on straight away if you are interested because they are only offering the new 2GB plan until 3/31/14.
It is unclear from their press release whether the 2 lines need to share 2GB of data, or they get 2GB EACH so that is something that needs to be answered. The fact that you do not need an annual service contract to sign up for this plan is noteworthy.