Sounds like you're in one of the few dead spots where Verizon isn't the best carrier choice to use. Is this your first Verizon device? If not, and if your other Verizon phones have recieved good signal reception then I'd suggest an exchange for another DX. The radio in the Droid X should recieve as well or better than most any other Verizon device, so if you're experiencing less than acceptable reception out of it the radio might be bad.
If not, then you may have to switch to another carrier/device in your area.