Honestly, I most often try to find a dumpster at a truck stop. At the truck stops without dumpsters but with only the compactor, I usually don't mess with the compactor and will go for a trash can at a fuel island. But it seems a little silly to me to put my trash in a trash can just so someone else can then take it to a dumpster, when I can skip the middleman and just go to the dumpster.
I very rarely use a dumpster at a pickup or delivery, and never without first asking permission. Trash pickup costs money and they may have a history of people (locals) dumping trash in their dumpsters, costing them extra for additional pickups, so they may be sensitive to it. The last thing I want is for them to view me or my carrier in a bad light.