John

I would do what Paul said but I would take an additonal step of capping the sprinkler heads where they are easy to get to with a half dozen of 1/2" PVC caps.  Then you are increasing the pressure on the leak and you will find it much faster and expend less water. 

Philip

HDR Remodeling Berkeley Ca

Check out this Houzz site for ideas http://www.houzz.com/outdoor-basketball-court

Do you have a budget? This would be the first question I would ask which also relates to your potential. You are looking at 15-20k typically.

Then are you looking at concrete or a rubber base?

Hi John, where are you located? It sounds like an expensive endevor to go artificial. How large is the grass area that we are talking about. This could help with the cost estimation.

Hi John, 

Turn on your sprinklers for the zone your leak is on and let it run. The area where the leak is will cause the ground around it to be soaked and water logged more so than any other area. There is your leak.

Good luck!