As others have already indicated, it depends upon which MLS you are affiliated with. Jay is correct that we receive TARMLS listing information via Listhub so long as you are opted in to have your listings included in their feed.
Also, please keep in mind that we don't just receive listing information via the MLS. It is also syndicated to us from other sources like Postlets, Point2Agent, vflyer and z57, to name a few.
And you can always submit your listing to us manually via the link below. It's easy to do and your listing will be live on Trulia within one hour.
Go to the "my listings" heading on your profile page. At the bottom of the list should be a tag that says "Not seeing some of your listings on this page? Try to find or submit them here." The later sentence will be a link to follow up and add them.
Hope this is Helpful! Have a great day!
I believe once you input your information on MLS, whatever sites use the IDX, will also have access to your information. Checking an hour after is good. Uploading additional info or pics is very easy on each of the sites, should you need to. Are you on ListHub? Many sites are interlinked, thanks to IDX. Hope this helps. Have a wonderful day!