Trulia takes feeds from various brokerage sites (such as Frank Howard Allen Realtors) and other vendor sites where Realtors submit their listings through. They do not take direct feeds from local MLS (such as BAREIS - Bay Area Real Estate Information System).
They also do not take open house feeds from the various sites I just described. What you have to do is to 'claim' your listing to attach the listing to you, the listing agent, and then on the right hand side, there is a button for entering Open Houses. You need to enter information about your Open House manually. I will give a couple days of lead time, which is not different than other sites.
There are a few quirks on Trulia but they are pretty new. I have the privilege of knowing this because I have been using Trulia from almost inception and watched their growing pains along the way.
Trulia Management , customer service, technical support, and social media guru are all very nice, talented, supportive and pretty amazing in what they have accomplished in such short period of time (coming from a technical background!)
Sylvia Barry, Frank Howard Allen Realtors
Marin Real Estate