70 minutes to connect, and switch airports besides? Not a chance.

traffic is not a simple good/bad, it depends on wx and all kinds of things but in general its crowded on the roads. while you'd be travelling "opposite" rush hour (and yes, rush hour starts just after 3 these days), the thing about this area is that there really isn't any difference between travelling "opposite" rush hour and with rush hour these days.

BTW, the hour to travel using public transportation was a surprise to me. although that will depend on the timing of your arrival and connections (bus to metro), etc but if you could do it in an hour, that's great.