Peachie, Are you on the October 8th Galaxy cruise out of Baltimore? MY DW and I are on that cruise.
The trip from the airport to the Seagirt Marine Terminal in Dundalk is about 30 minutes. The best bet is to jump a taxi at the airport. I dn't know the cost, but I'd bet it can't be more than $20 - $25.
We used a limo service and the cost was about the same as a taxi with a little better service. We used them both ways and have used them to go into Baltimore and DC at later times. The name is Private Car anf the can be reached at www.cincola.com or at 410/519-0000. I would recommend them highly - courteous drivers, spotless vehicles and no hassle.