We have found T-Mobile to be challenging in the S. CA area. Long Beach, Ontario, Rancho Cucamonga, Ventura, etc. You might have to go outside to get a good signal and the phone would occasionally not ring. Data speeds are slow but manageable. Our AT&T MiFi signal has been OK with only one weak signal area but the speeds have remained good even with multiple devices connected.
I have only been with T-Mobile for about 4 months and this is the first area where we have seen service problems. For the money we are saving, I am still a very happy camper.
