If I could give this a negative rating I would. I've used this facility roughly five times and each time it's a different hassle.
They're either closed at odd hours or swamped. The line has you standing in shopping isles. Nothing gets done properly.
Last time I went in they were in a rush. The woman guaranteed my letter would arrive within a specific time frame. She didn't want to deal with putting it through expedited because of the line behind me. My letter arrived late.
Trust me, save yourself the hassle and drive the extra mile or two to an actual post office.