It's imperfect, but you can travel with a very soft "language gradient": Extremaduran -> Portuguese -> Galician -> Asturian -> Castillian (Spanish) -> Valencian -> Catalan -> Aragones -> Occitan -> French ...
Each individual step is pretty easy, but it adds up to a huge difference.
Unfortunately, there isn't a great analogue for English. You can kinda construct a small jump by looking at Scots, but it ends quickly and is (at least to my ears) a jump on par with Portuguese to Galician.