If the weather permits, you can ride to Arisia and then park your bicycle in the Westin's garage.
The bicycle parking area is no longer in the closet.
There is space on the first level of the parking garage for parking bicycles.
Carefully walk your bicycle down the ramp (in damp weather it can be slippery). At the bottom of the ramp, go around the gate and go straight across the floor to the far wall (in the 1D parking area). There should be a bike rack there (or possibly near the handicap parking).