I've used the post office for money orders in the past. My only 
complaint has been the restricted hours.
The local banks charge way too much money for a money order transaction.
Super America gas stations and a local neighborhood gas station-grocery 
store-post office combo have been the most useful purchase sites for me 
and the cheapest.
The one vendor I found who sold money orders for $1 flat-rate got shut 
out by the money order parent company.

Doug.