[matese]

Do not use the retractable leash, use a 4-foot least, not a 6 ft.
A 4-ft leash you can pull him away before he can jump on anyone. I would try this for one month, then use the retractable, if he jumps on anyone go back to the 4-ft leash. I would keep doing this until he learns if he jumps on people, he loses his freedom and goes back to a short leash.
I must say I am not a big fan of retractable leashes when there are a lot of people and animals around, but I do use one in state park trails where there is plenty of open ground.