Well, I do not deliver Pizza....
But I prowl the night alone at a weekly hotel in Vegas running off the 'suspicious' traffic(drug dealer's, thieves and ho's). Babysitting grown adults that should know better. And then there are the drunks, the stoned, the homeless, the hopeless and those with major attitude.
I carry a Colt CCO .45 and I think it'd do fine for late night pizza deliveries too, but I might not wear the body armor, radio and ASP baton w Taclite for pizza deliveries. A decent folder, pepper spray, cell phone and several spare mags would accompany me(its my normal off duty load anyway). I'd change the ASP Taclite for a small Surefire.
Definately...keep your eyes open, NO matter what you do and where you are...you can go from 'all is well' to 'life threatening danger' in a heartbeat anyplace at anytime. Awareness is is more important than what caliber gun you have, and no matter what you have learn to use it well, subconsciously, close range and fast.
Have layers too. Pepperspray and a blinding light for non lethal options.
And watch out for groups of young men no matter what the skin color, the hyena method of manly fighting(where the macho youths gang up on the one lone 'coward') seems to be SOP.
Trust your gut/intuition and look for threats and avenues of retreat constantly....do not hesitate to call the Police for percieved suspicious behavior!
Some ideas.
Jercamp45