Hi,
thanks a lot for all of your help!
So far I've only got to try Brompton (which was too expensive) and Dahon Mariner (which I thought was too heavy). I will hit other stores suggested too.

Downtube Mini looks great. I'm gearing toward either that one or DownTube FS, b/c I have Specialized FS Mountain Bike and I totally love it (and it's cheaper too!). The thing about DownTube FS is that it's almost as heavy as Dahon Mariner which I tried today and I thought it was too heavy. But I found an article (http://www.foldsoc.co.uk/Mike/downtube.html) that says you can use one of its wheels to roll the bike around. Is that true? Other thoughts about DownTube FS? Thanks!!