Ok, this is my first post here, and I hope it is not too late to reply. I'm mexican and I live in Guadalajara, I have been to six flags mexico.
It is true that many kids here stop going to school to work, it is a sad social problem that the goverment is trying (or at least they say so) to fix.
It is not true that americans aren't welcomed here, but you have to be carefull because mexico city is really unsafe, so try not to wear your best clothes, just wear something informal, DO NOT wear any kind of jewrerly and try not to bring a lot of money with you while on the streets.
To answer your questions:
1) I drove from home
2) I'm not sure
3) I would say a 10, even thow this is a third-world country, the rides at Six Flags are verry safe.
4) I didn't go
5) Mexico
6) Mexican
7) I did feel unsafe in several parts of the city, so try to stay away from poor zones and try to stay in a good, zone (if you can understand me)
I personaly don't understand why do you want to come here, because we don't have the greatest coasters, but overall it is a fun place to spend the day. You probably won't have to spend 2 days in the park, just try to buy a flash-pass (they are caled the same here).
There are only 4 mayor casters in the park:
Medusa- a wooden coaster, I would say it's pretty fun to ride,
Batman- a standard SLC
Superman- a morgan hyper, the tallest, fastest, and longest coaster in latin america.
Boomerang- it was the first boomerang coaster installed by vekoma.
If you go, have a fun day!