I'll chime in here and share the soapbox on the spay/neuter issue. In this day and age, when there are so many potential pets being destroyed in shelters and abandoned around the world, it is amazing to me that people still question whether to spay/neuter a non-breeding pet (and don't even get me started on the "purebred" world).
People (and animals) get vaccines for two reasons: to protect themselves, and to protect the community. The reason that smallpox has been virtually eliminated is because of the vaccination efforts to combat it. By being vaccinated, you are performing a social good just as much as you are protecting yourself.
I see spay/neuter through a similar lens. By preventing your dog from being able to reproduce, you not only protect him from the health ills and behavioral problems that can lead to sickness and injury, you are also performing a social good that reduces the chances of more unwanted animals being brought into the world and having to be destroyed before they can know the joy of a loving home. One afternoon's absence and an unneutered male can easily encounter a stray or unspayed female and bring a whole litter of unwanted pups into the world, which overwhelmed shelters will have to house, feed, treat, and likely kill. A large social cost for such a small personal sacrifice.
To be quite frank, whenever I see an unneutered male dog or cat out and about, I lose tons of respect for the owners. With all the information that is out there, why people don't choose to spay/neuter as early as is reasonable is just beyond me. They are unwittingly imposing a social hazard on those of us who love animals and hate the reckless destruction of innocents.
I'll step down off my soapbox now. It's the second time I've come across this issue in the last 6 months (someone questioning the necessity of vaccinations and/or spaying-neutering their pet) and it aggravates me to no end. Trying to rationalize away one's responsibilities to society is so selfish. Not that that's necessarily the case in the OP's situation, but it's increasingly common in our "me first" world.