is this the D7 you are talking about ? http://boston.craigslist.org/gbs/bik/2393068837.html

it looks good and if it is really in a like new condition then the price of $300 is a bargain. see if you can haggle some more. go and check it out. that way you'll know if 20 inch wheel is a better fit for you. there are also 16 inch wheel bikes like dahon curve and curve sl. best way is to try the bike.