I think it's fair to assume that any house you're looking at will have air conditioning. It's such a common thing these days. It would almost seem wrong for a house to not have air conditioning. You should check with the realtor or with the owner just in case. But I don't think you really have to worry about it too much.
I believe this is a common error that trulia and other "real estate search systems " make. The listing agent should be able to go in and make the change , if not they should contact Trulia directly to help solve this issue. I would also ask how to avoid this in the future, then post for all of us to see. I hope this helps to answer your question.... more