I think I paid $10 at the UPS store for mine. It was real quick and I got 4 photos
Correction: The City Hall AREA in Chino Hills. My wife & I were the only one's there, and we were in and out in less than 30 minutes including all the paperwork. Of course we had or 4th expired PP so it was fairly easy. And yes, good only for those areas you mentioned, but good at any U.S. airport
got mine at walgreens too. really easy. they use a computer that makes sure the photo complies with the guidelines.
I remember I got the pictures at a machine at the Santa Monica pier. I also used it for my student Eurorail card. Ah.... good times. Apparently it you can just do it at the post office too but that is hit/miss. Don't put it off though and safe travels.
Walgreens is where I got mine, 7.99 for one, 50cents for each extra
Kinko's / FedEx. I had mine done there in Pasadena a year or 2 ago. $8 - 10 or so.
I do this alot for visa's, I get to expense it so I don't hunt too much for costs. CVS, Walgreens, UPS, Kinkos/Fedex all work great and get the job done. The specific post offices that do it are usually by appointment but work fabulous, just be sure to ask if they will take a photo at the time you make the appt.