Crossing the US-Mexican border can be a time-consuming affair, especially heading into the US. Canadians and even US citizens now require a passport to enter the US. Everyone else needs a visa or a visa-waiver. Whichever crossing you choose the procedures are the same, depending on what mode of transport you choose.
Crossing the border by bus can save time and money, depending on your destination, though customs checks are meticulous on both sides. Heading into Mexico, there is no US immigration check, but make sure your bus driver knows if you have a foreign passport – he’ll stop at the Mexican migración office so you can complete the FMM. After that everyone gets off the bus for a thorough Mexican customs check. Heading into the US, there are no Mexican checks, but everyone gets off the bus to walk through US immigration (passport check), before a US Customs check of bags and the bus (which can take some time). Further into Texas there is likely to be a US Border Patrol check, where officers will check IDs and question everyone on the bus.
If driving into Mexico, remember to pull in at the migración office to get your Immigration Form. You’ll also need to get a temporary importation vehicle permit (for details see “Getting there”). This must be dropped off on the Mexican side before heading back into the US. Cars also pay a toll crossing from either side of the Río Bravo. Heading into Mexico, customs checks are often very light, whereas the queues heading back into the US can be several hours long; a US Immigration officer will check your passport at a booth (no need to leave the car), and will direct you to park if he deems a customs check necessary. If there is even a tiny hint you are carrying anything illegal, US Customs officers will literally take your car apart and have sniffer dogs all over the seats – don’t expect them to clean up afterwards. You can also expect further US Border Patrol checks as you drive further into Texas, and army checkpoints on the Mexican side.
Crossing the border on foot usually means a walk over a bridge traversing the Río Bravo (for a small fee), connecting with local buses or taxis on either side. Heading into Mexico, there is no US immigration and often very casual Mexican checks – remember to stop at the migración office and ask for a “multiple migration” form or “FMM”. Heading into the US, you’ll have to clear US immigration (no Mexican checks), and often a full customs check of your bags.