They shut down the West Side bus stops shortly after 9/11 and apparently never re-opened them.
Just get off at Pleasure Island and walk over to Cirque.
When I was down in October there were several women on the bus one day who were going to the West Side and when we stopped at Pleasure Island, the driver very specifically said you had to get off there for PI and West Side, but they didn't listen and as the driver was going apst West Side they atarted pitching a fit, so the driver pulled into the parking lot and let them off at the old stop. I thought it was nice of the driver, even though it was the women's fault they missed their stop.