There is turboprop service still. It used to be relatively cheap (under $100 roundtrip) but as I checked today the cheapest fare is nearly $250. Ugh. If you haven't bought your ticket yet, you could always see if USAirways offers it as a cheap-add-on to another fare. Of course, then you'd have to give up United for a flight, which I can understand may be difficult
I would recommend a car unless you really don't like driving. I've never driven to Johnstown but you should be able to take major roads almost the whole way. If your conference isn't too long this will definitely be cheaper than limo service and you'll be able to get around Johnstown.
I've never taken any of the limo services so unfortunately I can't recommend any of them. If you haven't seen it, I found an unoffical website:
http://www.johnstownpa.com/
Good luck and let me know if you plan to spend any extra time in the area and I'd be happy to recommend other things to do.
BTW, I think the cheapest way would be to take the 28X bus downtown ($2 something each way) and from there take a Greyhound bus to Johnstown/Altoona and take a taxi from there.
[This message has been edited by pitflyer (edited 06-05-2001).]