
Personally I would have them off lead as soon as they show that they will be ok with each other. If on lead this is when dogs become more protective of them selves and of their owners. if they can't escape they will have to fight kinda thing.
Make sure that if you gve treats to your dog then you will have to make sure it is ok with the other dogs owner that you can give him a treat aswell so all is fair.
if they show any kind of agression be VERY firm (this will be unlikly on nurtal land!)
Rox