The image is fake, and is easily disproved using a reverse search. Ford shared the original photograph as proof for a 13 April 2014 "Ask Me Anything" session on Reddit, and the image at the time was clearly different:
The same photo has been digitally altered to show Ford's sign saying several different things:
Photo and sign aside, any speculation on whether or not Ford might be endorsing Trump was put to rest by a representative for Ford on 15 March 2016:
Ina Treciokas, Ford’s representative, confirmed to BuzzFeed News that the photo was fake. “He’s not endorsing him for president,” she said.