Whenever I am out and about, I look for a public restroom to jack off.
I have used restrooms in car dealerships, while getting my car fixed. This is the most fun as I sit in the stall jacking my meat, someone will come in to use the urinal. I can peek out through the crack in the stall and usually get a look at their cock as I'm stroking myself. I have gotton some powerful loads doing this.
I also like the restrooms in shopping malls and fast food restaurants to dump a load.