That's normal for AT&T for the last year or so all over the western US.
Their network is woefully overloaded and I doubt they'll be able to fix it for years. But they're an oligopoly and have no real incentive to fix anything quickly.
Everybody and their mom watching videos on their phones and tablets was an easily foreseeable problem, and they probably knew it was coming, but again, as an oligopoly, had no reason to care.
They've got hundreds of millions of reasons to care. I know it's easy to just take pot shots at AT&T (or Verizon). But both networks spend a ton of money consistently trying to build out networks ahead of demand. Data use has mushroomed in the last 10 years. Everybody expects to stream everything right now no matter where they are. Smartphones went from some hardcore tech people to grandma in the waiting room streaming Netflix.
Every big carrier knows if they fall significantly behind in service, they'll lose customers.