Just got the updated exhibitor info packet including updated info on all the hotels still available. Here are the ones that still have availability as of today under the contracted rate (and are close to downtown)
-Crown Plaza Houston River Oaks (4.5 Miles)
-Doubletree by Hilton, Houston Greenway Plaza (4.5 Miles)
-Four Points by Sheraton Houston Southwest (5 Miles)
Looks like nearly everything in the Galleria is open as well. Hope this helps!