Should you microwave tortillas in plastic wrap?

Not sure,  I'd put some kitchen towel around them when warming in the microwave.  

I try not to heat anything in plastic (or at least overheat) in the microwave. A damp paper towel under and over a small stack works best.

I do not know if microwaving food in plastic is healthy or not.

But having taken organic chemistry in university, and knowing that carcinogenic (cancer-causing) benzene rings are used in making plastics, I try to avoid heating foods with plastic (touching the food) as much as possible.

When they get hot, they will start to steam. 

All the Mexicans I know just zap them on a plate, or heat them on the gas burner of the stove.

No, I would wrap them in paper towels.

No.   Someone was pulling your leg.