Actually, it could be a hit and miss. I had ATT with two smartphones over 4 years including the Titan recently without a data plan. If I was to use my upgrade and get a discount on the phone, then a data plan would be required.
I was told by an ATT rep recently that if you are out of contract, you can opt out of a data plan. I asked this just in case Straight Talk did not work out for me and I had to go back to ATT. In the past, I actually had them block all data on my phone just in case. Problem with that is if you block all data, you block multimedia messages, but text are still fine. If they will no longer block all data, you should still be able to choose "pay per use" if you are not in a contract on that phone. Then you could turn the data off in the settings on the phone.
I now use Straight Talk, so I have data for the first time.