This is the "main" branch of the USPS on this side of town (or I think so anyway). This has been here for as long as ive been in this area of vegas (summer 1994).
Customer service as always been pretty good but lines can be fairly long as each person works at an incredibly slow, casual pace like no one in line has anything else to do.
The amount of people can highly vary. Sometimes empty. Sometimes a few. Sometimes a line out the door. Still can't really figure out when is when but I try to go around "non-peak-ish" times XD