They will need money. They will need a vehicle. They will need a place to stay out of site. They will also need things to attack with. All of this means that either they need to meet up with a hidden sleeper cell within the US or they need to contact someone who will wire them a lot of money, that they can get their hands on.
Based on all the questionings and immigration detentions that have occured, most of the high probability sleeper cells have probably been disrupted or know that they will be found out quickly if they help out in any kind of attack planning. This means that the FBI, might get a tip from a cell participant or the terrorists will be denied help.
OK, so do the terroist stowaways, just go down to Western Union and wait for their wire transfer? No, and the US government has really cracked down on a lot of phoney money movement schemes, so there is a good chance these guys might get caught trying to get money from an outside source. I have some personal experience recently that even bank fraud schemes to get money are being investigated at a very high level.
There may or may not be some terroists in the Country, but people are much more alert now and the methods of funding them that have been used in the past are drying up quickly.
This means that any terrorists will likely draw attension to themselves sooner. Hopefully with good police work, this will result in their capture before they do any harm. Remember that the last time the police had many of the terrorists in their hands, but let them go. Hopefully this time, they won't let suspects go as quickly
How about if the specially-trained terrorist stowaways meet some friends at a spot near the warm-water docks and are then transported to one of the nearby facilities indicated on the map ?
There, in the security of loving fellowship, they will have all the food, shelter, money and tactical support that they could ever possibly need.