I am in Yuma as well, and got an email saying that they had about 2500 doses for anyone over 65, but you have to call starting a 1:00 PM today to make an appointment. I started calling right an 1:00 but got the busy signal, so hung up and dialed again. I did this until about 1:30 when I got through to a ringing phone, but no one picked up and it disconnected after three minutes. When I dialed again, I got a message that is was a non working number, so I presume that meant that all the spots were filled.
I looked at my phone at the end of this and saw that I had dialed the number 180 times. Worse than trying to get tickets for a concert through Ticketmaster.