The Samsung Galaxy Proclaim and the LG Optimus Zip use Verizon's "Prepaid" network. Go to Verizon's website and check the map
for "Prepaid". It is a bit smaller than the full Verizon network. Note: These phones do NOT work in the Prepaid Roaming area either... just "prepaid coverage". The packaging on these phones are marked with a box saying "CDMA-V" on it.
The other Android phones use Sprint's "Prepaid" network - again, a bit smaller than Sprint's full network. Here is that map.
These should have a "CDMA-S" mark on the box.