The Fiesta is a fantastic car to drive. I bought a 1.0 turbo model, and liked it so much 6-months later we bought a 2nd!
I opted to dolly it mostly due to the cost of a tow bar setup, but also to have a dolly around in case one of our other cars needs a tow.
All Fiestas can be flat towed, no distance limit but they recommend staying under 70 MPH.
The Auto has be in Neutral. This can take a second to disengage the clutches, so be sure to wait for the "READY" message on the dash. Then after that, you have to disconnect the battery. But the Manual models just need to be in Neutral. No other steps needed.
The ST model can be flat-towed. They recommend against dolly towing the ST because the body work lowers clearance, but if you are careful, it can be done. Especially with a low-height dolly like the ACME.
