[jyl]

Coverage varies so much by provider and by location. Best to ask friends, neighbors, co-workers about the signal they get in the places that you travel, how often they get dropped, etc.

Then when you've decided on a carrier, have someone with that carrier (and a reasonably new phone) come to your house or workplace so you can verify they get a signal. It's that localized. Where I live, I can lose the signal on one block and have 5 bars on all the surround blocks. It'd be a bummer to find out your home is in one of those mini-dead-zones.

There are some websites where people report this stuff but don't know how much data they'd have for Modesto.

In general, Verizon seems to have the best coverage (says Consumer Reports) and I've found that to be the case where I live too, but it may be totally different in your neighborhood.

You might also look into analog capability, if you go into the Sierras or otherwise leave civilization a lot. I'm guessing that fewer and fewer phones offer it now.