Villazón and La Quiaca
The train station in Villazón is about 30 minutes walking uphill from the border (only a slight gradient but in heat and rare atmosphere can be a struggle) or 4 pesos (not accounting for inflation) Argentinian pesos by taxi from the border. You can take a train to Tupiza (4 hours), Uyuni (7 hours) and Oruro (16 hours). Trains leave 4 times per week. More information can be found at Ferroviaria Andina's website.
There is a 1 hour time difference between La Quiaca and Villazón of which you should be careful.
The more comfortable and faster Expreso del Sur leaves on Wednesdays and Sundays. The more basic Wara Wara del Sur departs on Mondays and Thursdays.
Prices vary according to departure day and class.
Train tickets for Salón class have to be bought the day before the train leaves (but they are kind of flexible about this rule) and for Ejecutivo they may be bought the same day. Trains leave 15:30 (3:30 p.m.) in the afternoon.
The old bus terminal in Villazón is 10 Minutes from the border. It's a straight road from the customs into the main town - keep going ahead and you will see the bus terminal. It serves only as a transportation hub for vans. There are plenty of ATM´s nearby. The new bus terminal is approx. 3km from the border. There are bus connections to Tupiza, Tarija, Potosí and directly to La Paz.
The bus terminal in La Quiaca is about 15 minutes walking from the border if you are fit and acclimatised to the altitude. If you have issues with heat, altitude or baggage, get a taxi which should only cost 5 pesos. The taxis are old and look pretty poor but get there without hassle.
Bus companies with a good reputation include FlechaBus and Balut. The trip is pleasant with great scenery. The buses are clean with toilet on board. Care is taken to protect your luggage. Safe way to travel. However, avoid buying a "FlechaBus" ticket from an office that says "FlechaBus", unless you are completely sure that it is the right office, because otherwise they will likely betray you! (And beware, you cannot always trust the bus line names written on the sales offices.) Touts in La Quiaca will try to lure you into that office. Their scams include selling you a bus ticket which is not for FlechaBus but actually for a different bus company of lower quality like Panamericana (of course for the price of an actual FlechaBus ticket). They may also sell you a combined ticket of a different bus company (e.g. "Arco Iris") and tell you, that bus takes you in 15 minutes to a place where you change to a FlechaBus while you will actually spend several hours on that first low-class bus (no air conditioning nor bathroom) and have a FlechaBus only for the last small part of your trip. Wait for the actual bus of the desired company to show up, if you're not completely sure what office books what bus. Be aware that an office may sell you different companies' tickets even if the office looks like officially belonging to a specific bus company (e.g. the office labeled "FlechaBus" in big letters will likely sell you some lower quality bus lines' ticket for the price of a "FlechaBus" ticket and even lie to you if they sense that you are suspicious of not getting the service that you paid for)! Avoid Panamericano as they charge a hidden "gringo tax", sell overpriced service to Salta that changes bus lines in Jujuy, and the bathrooms on their buses do not work. Also to note concerning Panamericano, do not purchase tickets to further destinations than Jujuy, e.g. Buenos Aires. They appear to be the cheap and claim they involve a bus change at Jujuy however they are fake and only get you as far as Jujuy terminal at which point all the terminal companies there will inform you that you have bought fake tickets.
If you are going into Bolivia - To walk from the bus terminal to the border - from the corner of the bus terminal, turn right on Belgrano street. It's about 5 blocks (or less) straight down to a T-junction (wider main road boulevard - Av Internatcional). Turn left when you reach the t-junction of this main avenue. It's another 100 m from there to the border customs (you will pass a gas station). Reliable information on bus tickets for Argentina and Bolivia routes are available at AndesTransit.
Villazón is separated to La Quiaca by an international bridge with Bolivian immigration on one side and the Argentinian on the other. The border procedures are fairly easy for most tourists.
As La Quiaca is basically a boarder crossing town it is not a tourist town. It has a safe feeling. It seems to be progressing as there is a lot of building reconstruction around the centre of town. It would appear to be a town that is thriving on exports to Boliviar. At the border crossing there is an army of Bolivian people taking heavy loads of goods across the border. It is possibly easier to have the army of couriers take the goods by foot than to get the goods through custome by truck.
The border crossing from Argentina to Bolivia is not a big deal anymore. All Bolivians can cross the border without Immigration, there is no long queue anymore. You will get your Bolivian Visa printed on a paper (for 30 days) from the Argentinian Immigration office, you won´t get a Bolivian stamp in your Passport. There is no shelter where you queue - at high altitude the weather conditions are harsh and can change rapidly.
There are hearty and cheap menus available upstairs at the municipal market, from about Bs 8. Around the bus terminal, there is an abundance of reasonably-priced eateries. For better food you have to head to La Quiaca. Watch out for restaurants refusing to give prices, they charge a lot more if you don't agree a price beforehand. La Coyote near the bus station down towards the centre is very basic looking but has good prices. A full meal can be had for $48.
There is an abundance of cheap hostels between the bus terminal and the railway station, so accommodation will not be a problem.
Hotel de Turismo. 140 Argentinian pesos per night (October 2009) is reasonable. The standard is as good as it gets in town, close to shops as the town of La Quiaca is not too big.
Hostal Plaza is a decent, reasonably clean hotel with hot water. It's on the main square, and costs about 150 bolivianos per night for a twin. 135 for a double.
Hotel Centario. 100 Bolivianos per night (January 2015) for a double room with private bathroom. Close to the Bolivian bus station. Just cross the street and take the first right (La Paz street). After 50 to 100 metres you will find this fine hotel. Which is fairly new and well maintained.
Note that there is NO access to wifi in Villazón. There is one Internet cafe that advertises it (on Calle Independencia, a couple of blocks up from the main square), but they claimed it wasn't working when we tried to use it. There are, however, several Internet cafes that charge about 3 BOB an hour. You just can't use your own computer.
There are two ATMs that take foreign cards in Villazón, both on Calle Independencia - one on the Northwest Corner of the square - Banco Unión (beware: it charges 5% on withdrawals) and one that is quite hidden, about 5 meters further up (I don't know if this one charges extra).