Corn harvest here in Ontario, been a little busy at the elevators and I missed this question. Four a.m . starts to a riding day is inhumane, no way to treat yourself on a vacation. Take it slo'n'easy , ya get there when ya get there. These big city border crossings are open 24/7 and they have some staff for Migracion and BANJERCITO on hand all the time .But limit yourself to the normal waking hours and you will do fine. And yes , you are perfectly legal to go to a Nvo Laredo hotel for the night , 72 hours in fact, before you bother with the customs formalities. If you look at the Migracion terminal's parking lot as you cross the bridge you can gauge how busy it is . I gather you are crossong on some kind of USA holiday , but you might be surprised at the dearth of cars at that office. If there is a crush of traffic on the bridge it does not mean they all want customs processing. Lot of them are crossing to do weekend shopping , a bunch are going over to just get drunk and others are going to visit family in the city. None of these groups are going to do much in the way of document processing . If you do it later in the evening you may find the terminal practically deserted and be served quickly .