Correct. If you don't talk the Jarl, no dragons
Cool I won't talk to the Jarl.
You can use the console commands on PC and give yourself 1,000 dragon souls and it stops random dragon spawns. 360 and PS3 don't know what to tell ya. When and if you do want to get into dragon spawning land you need to remove the 1,000 dragon souls (or at least reduce it o.O)
tl;dr Only way I know for sure to stop dragon spawns is to have 1,000 dragon souls /shrug.
I'm on PS3, I got the 20 needed for my trophy so I'm happy not to fight dragons again, at least not until I play the MQ again.