A week or so later, a second mailing came from the city. It also didn't say how the pickup days were changing, and it also said to watch for a further notification in the mail. It didn't say to call in, and it didn't say to check the city's website.
No further notification came. Everyone in my neighborhood apparently continued to put out recycling and garbage bins on the same days, and they didn't get picked up. Kat called today, and the person answering the phone for the City of Phoenix waste disposal said that they did no specific mailings, rather, they expected people to "get curious" and either look online or call them.
Well, we did indeed "get curious" as to why our garbage wasn't picked up, so I guess their expectation was valid. My initial assumption was that we had a new garbageman who didn't know my house was on his route, since I've had to call a few dozen times in the past about garbage and recycling not being picked up for that reason.
I've put out the recycling bin for pickup tomorrow--next to the full garbage bin that will be sitting out there until next week. So far, none of my neighbors have done the same.