Thanks for the cross-post Rusty!
Okay, so on Tribal law I need to be more clear than I was before. I think I was a little muddled and I've brushed up quite a bit about it since my last post.
Every tribe has their own laws governing firearms carry, and some of the tribes (Apache) are quite welcoming of carriers, while some are not (Dineh "Navajo"). The safest rule to follow when you're crossing tribal land is to follow the Navajo rule, just so you're not caught out and in violation of their laws.
The Navajo rule is the same as the Federal safe-passage rule, which states that "persons traveling from one place to another cannot be incarcerated for a firearms offense in a state that has strict gun control laws if the traveler is just passing through (short stops for food and gas), provided that the firearms and ammunition are not immediately accessible, that the firearms are unloaded and, in the case of a vehicle without a compartment separate from the driver’s compartment, the firearms are located in a locked container." -stolen from the Cornell law site.
You can stop for food or gas, but you shouldn't be stopping for vacation on tribal lands if you want to not be in violation of this rule. Also, what that bit doesn't cover is that you can't have the firearm locked in the glove box, or a locked center console. Those areas are still considered immediately accessible.
In the Phoenix/Scottsdale/Mesa area I've crossed the Salt River reservation on McKellips a few times open carry in the past(before I was aware of the tribal law differences, and discovered that McKellips being part of my commute doesn't protect me), but the SRPMIC is likely going to come down a lot harder on non-tribal-members crossing the reservation after some recent officer-involved shootings during traffic stops. Nowadays, when I'm making my morning commute, I just stay on the 202 and the 101 to avoid the reservation.
If you are crossing this reservation (and it's easy to do without realizing you are - SR-87 crosses a big chunk of reservation land), then you might want to study up on these parts of the tribal law:
The full text of the tribal law for the SRPMIC can be found here:
http://www.srpmic-nsn.gov/government/ordinances/files/Chapter6.pdf