Hello; advice & help would be welcome for my folding-bike pick.

I'm shopping for a folding bike for my commute from Baltimore to DC. Currently my commute involves several periods of walking, a usually-reliable light-rail ride, a commuter train ride, and a subway trip! I'm hoping that a folding bike will help connect the dots between the various kinds of train rides. Maybe I can also replace the subway and/or light rail rides with pure biking -- the distances would be okay for biking, just not for walking all the way.

I've mostly settled on the Dahon, but their site seems organized by performance instead of by task. I also can't tell if a bike might be appropriate for commuting just b/c it doesn't come by default with luggage racks etc. Also, b/c this will be my first folding bike, I don't know if 16" wheels will drive me nuts when trying to bike 3 miles?

My needs: It needs to fold up as small as possible, be reasonably light, and be able to withstand LOTS of bumping and carrying through large crowds. I'm used to carrying most of my stuff in a backpack, but at least one luggage rack may be necessary. Mud guards are a must and chainguards seem wise if there's a chain. -- but maybe a hub would be best for these condition?

If I nix the light rail, I'll be riding 3 miles -- mostly downhill in morning, uphill at night, if I do that -- this is Baltimore, after all.

many thanks for all advice!