Brian,

You're going to be about 10-15 minutes from Ridley Creek State Park. There is a loop in the main park. Hilly but a nice running location this time of year. Google will get you there.

Mercer

This guy lives in the area. He runs badwater in a pink tutu. Some of the local runs I know about:
Tuesday, 5:30 am: Conestoga High School, Track workout
Wedensday, 5:30 am: Lancaster County Farmer's Market in Wayne, nice and hilly 8.3 mile loop (coffee and whatnot at the market afterwards)
Friday, 5:00 am: Wegmans in Malvern, flat 10 mile up and back (coffee and whatnot in the cafe afterwards)

Check out Valley Forge Running Company web site for some other group runs.

If you want to venture out on your own:
Ridley Creek State Park, lots of trails plus a paved loop
Schuylkill River trail, mostly flat
Chester Valley trail, mostly flat
Valley Forge National Park, hilly 5 mile loop plus some trails