My suspicions were correct. I noticed that my phone was reporting the incorrect phone number. One digit was missing from "Settings"/"About phone"/"Status"/"My phone number". Standard MetroPCS customer service wasn't willing to help me until 72 hours had passed since my number port. Today, I finally got them to help me (but only after they tried to transfer to the porting department which was closed at the time and they didn't believe me when I told them this!). They helped me edit the settings on the phone and enter the correct phone number. And, voila! Google maps worked immediately and after I re-entered my gmail password and turned on synchonization, gmail worked too. I just downloaded the ITA OnTheFly application which I'm excited to try out since I know one of the developers.
I wish MetroPCS had separate "smart phone" agents (not to mention a less crappy automated voice menu navigation system). The agent that helped me gave me instructions which often were somewhat confusing or unclear because I have a smart phone. One example is when she asked me to dial a number to put the phone into setting-editing mode. She just told me what to dial without indicating that I needed to open up my phone's dialer. Of course, I quickly figured out what she meant, but dealing with customer service is hard enough as it is---having to translate from normal phone terminology to smart phone terminology just makes it more difficult.