I've hiked through the Zen Center numerous times and have never asked permission. It's always been my understanding to remain silence when passing through the Center out of respect for those meditating and I've never had a problem. I've always parked outside the gate. I wouldn't know whom to call.
I highly recommend the hike from Hwy 74 via the PCT to either Idyllwild or the Tram to anyone looking for a good marathon adventure. It's not as much in the way of elevation gain as the Snow Creek to the Tram trip but it's a bit longer.
