With "normal" dog I would definetely wait until dog reaches maturity, however dogs whos testicle(s) are left inside might develop some health problems (infection, tumor...) so I'd check with vet in regards to how long you should wait. You can also have testicle surgicaly taken out, but you shouldn't breed that dog as it is hereditary condition.
Originally Posted by zedandme
As for the breeder, you can contact him, but I don't think you can do much about it. Although it's hereditary, sometimes these things just happen.
Respect and you shall be respected. Animal is always right.