Here's the deal - the Marriott has set up two blocks of rooms for Jamboree. One is $160 per night single/double, and the other is a smaller block on the Concierge level of the East Tower at $180 per night single/double. Concierge guests receive a free hot buffet breakfast, hors d'oeuvres, and soft drinks served in the Concierge Lounge. The tier pricing, and the number of rooms assigned to each tier, was set by the Marriott. To date Wednesday night is sold out for both tiers, Thursday night is sold out at the lower tier with the concierge tier still available, and both tiers are available Friday and Saturday nights.
If you have tried to make a reservation online and received a "no rooms available" message, don't despair. Rooms may be available, but at different tiers for different nights.
Here's what to do if you get a "no rooms available" message. Call the Marriott directly at (818) 843-6000 or (800) 840-6450 and make your reservations over the phone. Mention the group Genealogical Jamboree 2015 to get the Jamboree block prices. The room blocks close May 13, 2015, or when the rooms are sold out --which could happen in the near future.