Another question:

The gate valve in the PVC pipe at the top of the photo turns on the
water supply. The second one does nothing as far as I can tell. Would
that be part of a vacuum breaker? Should I leave it closed or open?

Check out the photo he
http://www.flickr.com/photos/d=ADavef/10459050/

I have heard that a vacuum breaker is required to keep irrigation water
from being sucked back into the water main in the event of a water main
break.Though I suspect that this system is on pressurized irrigation.
How can I tell. The irrigation company is so busy this time of year
that they haven't called me back. My neighbors are clueless.