The rate at the conference hotel, Loews Ventana Canyon Resort, should be $139.00 (plus taxes, which will be added) per night. You can reserve a hotel room at the conference hotel, Loews Ventana Canyon, using this link or by calling the hotel at +1-800-234-5117 (and be sure to mention ACM/SPLASH). Even after the early registration deadline you should still be able to make a reservation with the hotel.
Loews is still accepting reservations for the nights of October 21-24, which are what you would need for the main conference. However, the Loews Ventana Canyon hotel is fully committed for the nights of October 19, 20, and 25, so if you want a room for one of those nights they can only put you on a waiting list. If you are staying over some of the nights that the hotel is sold out for, then you might need to stay outside of the conference hotel at another hotel during some nights.