Factual error: When Garrison takes a phone call at the Mayflower, the person on the other end tells him to "walk 3 blocks east on Massachusetts Ave., take a left on 12th Street, Las Palmas coffee shop." The Mayflower is at Connecticut Ave. & L Street, about 6 blocks directly west of Massachusetts & 12th. Massachusetts Ave., which runs diagonally, does not form a logical route between the two locations.
Continuity mistake: When Eva Longoria first appears on screen, you can see her on a CCTV monitor, she then passes through the door, and the camera moves slightly to show her physically going through the door. You can still see the CCTV image and can see the door is closing, but when you look at the physical door she goes through, it's not moving. It's supposed to be the same door.
Plot hole: Right at the end when Pete calls for the "Hard Car" to evacuate the president, he gives very specific orders as to the evacuation point. Considering he was to be arrested on sight, there is no way he would know any of the security arrangements and they would surely have changed them radically because he was such a senior agent. The Secret Service is constantly changing their security.