I've been liking the Paselas for all my 27" wheels whose frames can accommodate the size, it is what I put on our bikes for a CC tour for a combination of everything from footpaths to roads (albeit no real tough off roading). They're pretty much a default install for all my bikes now. I can generally find them under $20 each with a bit of patience, but Niagara has both the 700x35 and 38 for $24.99 right now.

EDIT: Not foldable, though.