Cingular coverage? Partner coverage? I'm confused.?

It just means you will be roaming. Using another carriers towers. If you have free roaming it will not affect you. Most people only know they are roaming if they have their phone set to ask everytime they are in roaming. It is only something to worry about if your plan does not include free roaming. It can get really expensive, besides paying roaming charges you could be stuck with long distance while roaming also (when you are in roam you do not have long distance coverage free) But...if you have free roaming you have nothing to worry about! ; )