I had to go back to the lot at the Chevron station by I-505 to listen to a conference call one day. I have Sprint. I did get a blink of service closer to the creek by the curve at the orchard.
The hill just above Lake Solano on Pleasants Valley Rd is where I go to get reception. I can get a pretty good signal there. Other than that it's pretty much hit and miss near the creek for me. If it helps, I have Sprint.
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"Nothing makes a fish bigger than almost being caught."
I have nextel and no I don't get reception. Occasionally I will hear a chirp briefly with a quick signal. I stopped bringing it when I fell in and got it wet, pretty smart to bring your cell phone on the creek when it does not even work.
Just a note on dunking cell phones and cameras. After dropping a lens in Putah Creek I search the net for some way to protect them and found a site http://www.aquapac.net. They make waterproof containers that float. You can even take pictures through the case. I bought one for my camera and one for the phone and they have worked fine.