Okay, on a saxophone, a leak has to do with AIR, not saliva. If the pad leaks when closed, the saxophone will not play properly. Your problem is with a buildup of saliva. Saliva will often collect in that part of the saxophone, and will come out those keys when open. You can reduce the amount of saliva that goes into the horn by refraining from eating before playing. This includes any gum or alcohol as well. Between songs, you could also open the left-hand palm keys and blow at them to remove some of the moisture. Holding the horn more upright might also reduce the amount of saliva that comes out of those keys, because it might move down into the bell instead, from where it can be poured out.