Niki from Trulia Customer Service here. We do not have support for Mac IPhoto in our resources.
When you get to the upload step for pictures, in the listing edits or your profile edit, you will need to know the folder location used by IPhoto to choose the file you are uploading. There is no direct upload to the site using your camera or the photo management software. Save your pictures in an easily identifiable place in your computer and the browse button on our site should allow the file to upload on Trulia.
Please feel free to contact us directly by email at firstname.lastname@example.org or by phone at 1-888-466-3501, Monday - Friday 7am to 4pm PST.