I tried browsing the at&t site, but it doesn't seem very helpful.
I have at&t, and a good friend of mine also has at&t. She is traveling in italy for 10 days. She spoke to at&t CS before she left, and was told that incoming SMS from the US will be deducted from her standard messaging plan (she has unlimited texting), but there will be a cost to send from Italy to the US. I cannot find any information on the at&t website to verify this. She told me to text her often because its free to receive. I just don't want any surprises when she returns.
Also, it is $0.50 to send, correct? And if I have Unlimited Text and send her an SMS, it is free for me?
From personal experience I say that the information you were given is correct. Incoming messages draw from the normal domestic text plan. Sent messages for the person whose phone is abroad are $0.50 each to send.