If you neuter dogs after 5 mos, they already have all the ahem testosterone poisoning and behavior changes may be minimal, but should help not responding to bitches in heat. USUALLY helps prevent marking if the dog hasn't already started.
I worry about Cara having pediatric neutering… I know rescues have no choice but I have become more and more of a believer in NOT doing full spay/neuters or waiting til at least 18 mos for their health. Sadly the research is becoming pretty clear that other than bitches with mammary cancer, the health issues clearly are on the "no neuter" side.
Dog management is another issue. And yes, I think it is the only responsible option for rescues. But there is now a shot that keeps ALL MAMMALS from getting pregnant for at least 5 yrs. I hope it is commercially available soon. (basically to changes the egg surface so that it cannot be penetrated by a sperm)
For some pretty clear discussions on neutering:
As for your dog, it really depends on how old he is and what his behaviors are now. If young, most behaviors will have to do with maturing and not necessarily having been neutered but at least it helps avoid the marking and wanting to go find a local in season bitch. :) If older and already has behavior issues, the decreased hormones help a little but you still have to train and address them… just neutering won't help much.