Well, figure out if you want to try it and if you can make it work. Liability is a valid concern, but we're all big boys--we'll sign something if need be.
Check out my web site at www.rallystuff.com.
The Celica lives in West Chester, so Chester county is cool. Brad, the Golf driver, has a temp page at www.rallyhawk.com.
The same shop we use in West Chester also services a ProRally Porsche 914-6. There are MANY rally teams within an hour or so of Philly that would be happy to trade drives/rides for the use of private testing grounds.
The key for testing is having at least 1/4 to 1/2 mile of reasonably smooth surface--dirt/gravel road or grass--that nobody minds if it gets rutted-up.