Best overland route from Lima to Tucuman, Argentina?
 

I want to travel overland by bus from Lima, Peru to Tucuman, Argentina through Chile or Bolivia, and need advice on the best travel route. The trip should span 6 weeks, so I can see some things, and not be exhausted by long bus rides. I will consider train segments, if they are popular, efficient and affordable. I will be staying at hostels along the way, and would appreciated advice on these also.

As no one else has pitched in, I'd recommend you go south to Arequipa and then up to La Paz, Bolivia, then south to Tucuman. Since you have plenty of time, you might consider detouring from Puno, Peru, to Cusco Peru and seeing Macchu Pichu and the other fascinating sights around Cusco. There is a train between Puno and Cusco and one between Cusco and Macchu Pichu. http://www.seat61.com/Peru.htm

Other than the routes around Cusco Peru, and a couple of other tourist routes, I would be very surprised if you could go much of anywhere in southern South America by train. While I have not been to Bolivia, the busses in Peru and Argentina are very good, inexpensive, and comfortable, so I would advise you to take them.

In South America, it is customary to take overnight busses. Far from exhausting, they offer very comfortable sleeper seats--much more comfortable than tourist class on an airplane-- and save the cost of a hotel room.

There is a train that runs a few x a week from Oruro to Tupiza. But you need to combine with bus and taxi from La Paz
Also a train Tupiza to Villazon.

Check Kanoo Tours website for other options. They are a good budget agency in LA Paz.


Bolivian buses are not very good, even the tourist ones.

We have done the route from Lima to Salta, just north of Tucumán a couple of times by different routes albeit over a longer time period.
The most straightforward way wit the most to see is probably:
Lima
Cusco
Titicaca (border crossing to Bolivia)
La Paz
Uyuni
Tupiza
Villazon / La Quiaca (border crossing to Argentina)
Salta (via juyjuy)

Buses are great in Argentina and Peru (overnight is fine) but generally pretty bad in Bolivia (avoid overnight if at all possible)
Train is an option from Cusco to Puno but expensive (I also read recently that perurail are running a service all the way from MP to Puno). In Bolivia trains are a good option if they fit with tour schedule but they don't run every day.

Te best thing to do is get a guide book(s) and identify which sights tpyou want to see and then see how they fit into and itinerary. Six weeks sounds like a lot of time but there is a huge amount to see in the regio, so you are going to need to be selective. The more planning you do now, the better.