Thanks for all of the replies. I am still a bit confused because it sounds as though Spirit of America does have a cellular link when at sea.
Even though I have a "nationwide" plan with no roaming charges from any US cellular tower, it looks like I will have to wait until I am ashore to guarantee no extra charges from NCL.
Read and post cruise reviews
NCL - Pride of America - May 2011
Carnival Elation - February 2011
Carnival Elation - November 2010
Carnival Dream - October 2010
RCL Oasis of the Seas - May/June 2010
Carnival Fantasy - April 2010
HAL Ryndam - September 2009
Carnival Holiday - May 2009
Carnival Celebration - April 5, 2008
Carnival Liberty - May 2007
Carnival Miracle - April 2006
Windjammer Fantome - 1987