Tacos de Cachete in Phoenix Area
I believe the barbacoa tacos at the El Taco Tote chain are made of beef cheeks. The ones at their Mesa location tend to be a little too fatty for my taste, but the ones I've had in Tucson are great, so perhaps their other Phoenix area locations are good too?
Lulu's in Gilbert has sesos and excellent lengua, but I don't remember cachete; you could call and ask. I know neither Guedo's nor Los Taquitos has them.
Lulu's Taco Shop
610 N Gilbert Rd Ste 302, Gilbert, AZ 85234