The Amtrak solution would probably be the nicest if you can't get a good rate on a one-way rental. I've taken Amtrak from PIT-Penn Station and its always been a very comfortable ride, and if you've never ridden the trains before a whole different experience from planes. I'm not sure if Johnstown is before or after all the beautiful scenery on Amtrak's route through PA... but it should be nice, if you have that sort of time and the train schedules work out. I'd give yourself two hours from arrival at PIT to get to the train to be safe; it's about 30 minutes to get downtown from the airport via bus, assuming you don't have to wait long for a bus.

We can either meet at the airport on the 7th or meet nearby at a place like Quaker Steak and Lube -- a good local chain....