The Aztecs and Mayans do have steel weapons - at least, they do in the game - otherwise, they wouldn't be able to make Champions, or other units.
You can always take a Jaguar Warrior, or an Eagle Warrior, and rename it. The only disadvantage is that those units cannot auto-heal. For other heroes, you'll have to make sure you don't take a horse-based hero. I recommend:- Any Hero that is normally accessable via the Aztec or Mayan Tech tree;
- Axe Thrower-based Heroes (Mark Stoker used one in Nyctophobia, and for some reason, they are quite appliable in a jungle scenery);
- Samurai-based Heroes (may seem a bit out place, but with a little imagination, you can make a lot out of them);
- Longbowman-based Heroes (there's not a lot of difference between Arbalests and Longbowmen if you look at their appearance);
- Woad Raider-based Heroes (they've always looked a bit shabby to me - maybe you can do something with it).
Hope this helps.
Luke