It's not the leash that freaks him out. I have a divided yard, and he has no problems walking on the leash in the fenced-in area. Sure, he may pull, but he walks. However, when I try to take him for a walk outside the picket fence, he just lays down. No amounts of coercion/treats have convinced him to keep walking. Obviously I don't want to pull, but the boy needs exercise! Any suggestions as to how I can get my dog to go on walks?
Okay. More details.

He's an 8 month old Boston Terrier. I am the original owner. I live right on Lake Erie, so part of my concern is that he may be afraid of the sound of the water. Sounds silly, but who knows.

So still a puppy. Small dog. And he's always been mine.
Still more details. I've tried both a harness and a head-collar. He still lays down.

Try food, I kid you not, small dog bikkys or treats in your pocket. When you get out the front gate, give him a palmful, then move afew steps, give him more, then walk further on, give him more. Don't over do it, of course, exercise is meant to get rid of flab, not put it on See how you go with this.