Thanks again for the additional replies.

Bikes over $1,000 are a little out of the price range.

Terry at RideThisBike.com is recommending the Montague CX 16" frame with 26" wheels at $495 and 29 lbs.

Regarding traveling on a bus - being able to put the bike in a bag in the luggage space below, and not carry-on is what we had in mind.

I am surprised there is no sticky thread in the Folding Bikes forum that has a list of the current USA sources of folding bikes : BikeFriday.com and Montagu at RideThisBike.com I knew about, but not;
Birdy at http://blackdogbicycles.com/birdyfoldingtravelbike.html
and http://www.dahon.com/

For myself, I was set on a bike that folds quickly for everyday train commuting and the Montague Paratrooper or Swiss at RideThisBike.com looked good, but now I'm tempted by the Dahon bikes - wow. Expensive, but soooo desirable!