We just completed a 6 day visit to the Copper Canyon. 
Much of the canyon is only accessible by
Rail. The Chihuahua al Pacifico division of the Mexican National railway runs passenger service from
Chihuahua to Los Mochis, Sin. (400 miles) There are two classes of service; Primeveria or First
Class and Segundo or second class. The second class is definitely native. You will be lucky to get
a seat, the windows are filthy, and I doubt there are any functioning bathrooms. On the days we were
in the canyon the segundo had many freight cars with locals riding on or under the cars.
The first class train is, however, a different story. While it is not First class by American standards, it is perfectly acceptable; the cars are clean and roomy and the windows, for the most part, were reasonably clean. We do suggest that you bring your own toilet paper however. The train leaves daily from each end of the line. While you can do the entire trip in one day, it would become very tedious. We dealt with a Mexican travel agency in Chihuahua (Turismo Al Mar) and they put together a dynamite package for us.
We left from Chihuahua in the early morning (7:00) on Train #74. 
The consist was three coaches
and a GP 38-2. This was typical of all of the four trains we rode. Although a few had GP-40
locomotives. The coaches appeared to be ACF or PS vintage but had been modified with generators
for hotel power. The crew size was large by any American standard. The operating crew included
an engineer and fireman, conductor, at least three assistant conductors, and a rear brakeman. The
brakeman seldom left his post at the rear of the train, especially on the mountain runs. The service
crew was also large, but except for food service, you generally did not see much of them. 
The Chiefs of On board services generally spoke passable English and they made announcements along the way regarding upcoming scenic vistas or notable railroad features. The remainder of the crew consisted of three armed (carbines and automatics) special services troops. At least you feel secure!
The crew allows riding in the vestibules, and with Dutch doors, this is clearly the best
viewpoint. The food service was minimal, consisting of sandwiches, candy and drinks. (All reasonably
priced and brought to your seat.) 
Many of the stops have vendors selling all types of food,
both hot and cold. Use your own judgment. Bring your own water to drink along the way.
The line is single tracked, non signaled, and has sidings every 15-20 miles. During all phases
of the trip, meets were made at many of the sidings. The route appears to be quite active
with both local freight and TOFC. 
There are many station stops in small villages where the
train is obviously the high point of the day. At the halfway point is a town called Divisidaro.
Passengers may detrain here for a 15 minute stop. Many food items and local Indian crafts
are sold here. In addition, it the first view of the canyon.
The passengers were a mix of gringo tourists, a smattering of Europeans, and a lot of natives.
Our first day ended at Possada Barrancas at 2:00pm. 
We spent the night in the most
unbelievable hotel, where all the rooms have a balcony looking directly into the canyon. The
canyon is larger than Grand Canyon, but probably not as spectacular. This is, of course, a
subjective opinion, but you don't see the vivid red colors of the Grand Canyon.
While at the Hotel we went horseback riding for two hours up to the top of the Canyon rim.
The guide, Cecilio, spoke no English, but it didn't matter we had a great time. Later that
afternoon we caught the westbound train and continued on to El Fuerte. From a scenery
standpoint this is probably the best part of the trip. 
Tunnels, switchbacks and long or high
bridges are also interesting. Just east of Temoris, the route goes through a 180 degree tunnel
followed by a triple switchback. For an easterner, this was an unbelievable view. The train
arrives in El Fuerte about 7:00 PM. We stayed in an old Mexican hotel that was really great,
Posada Del Hildalgo. The next morning we boarded an eastbound train to start the return
journey. We spent that night in Creel, and had an interesting tour given by our Taxi driver,
Rafael. If you have time and the inclination, consider a trip from Creel to Batopilas which is
at the bottom of the canyon. This requires an extra night, but I understand it is worth it.
The next day we arrived back in Chihuahua. We heard horror stories about Mexican railroads - both reliability and comfort. All four days the trains were within an hour of schedule, usually less, and the cars were acceptable. The bathrooms do start to get a little bad by afternoon so that can be a problem. We would do the trip again, and had a great time.
The entire package with some of the meals included was about $500 for two people. This included 5 hotel nights (2 in Chihuahua) and the train tickets. The paperwork was delivered to our hotel the afternoon we arrived (No deposit required.) You can call the Travel agency at 52-14-10-92-32 or 52-16-59-50. They are there on Saturday morning when the phone rates are cheap. Arturo and Hector speak English, though I think others do also. They did charge a slight premium for the train tickets, but considering the effort it is probably worth it. We have found out that if you write to the railroad you can buy the tickets direct.
Address is:
If you need any other info, feel free to contact us. We would suggest you get a guide book. AAA is great for information on Mexico in general as is the Lonely Planet. The Fielding guide is so-so.