It couldn't hurt to try. What's the worst that could happen?
It's good to hear that you've found so many really good folks working for the U.S.P.S. in your area. In over 28 years as a Postal Worker (as opposed to a "postal employee", if you see the difference), I've found that there are many standouts like that, folks who actually care about the customer. I like to think that I'm in that group, even though I work in a sorting facility and have no face-to-face interaction with customers. My local P.O. has no off-street parking, yet I'd rather go there than the one at the plant where I used to work. Lines move well, the clerks are polite, and things I sent from there are always handled gently, at least where I could see them.
I still cringe when I think about the videos I've seen on YouTube shot by security cameras of UPS deliverymen just tossing packages over fences or onto porches, or left out in the rain in puddles, etc. There are always Postal delivery supervisors out on the streets keeping an eye on carriers at random, and if a carrier is seen doing something like that, they may well find themselves out of a job... until the union steps in and gets them their jobs back - with back pay. Management usually wimps out when pressed over these things.