I have gotten a safe to pass left turn signal in Quebec from a trucker,,, once, maybe it's not just a courtesy in Mexico.
We've taken six trips in Mexico since 2013 on a motorcycle, logging in over 20,000 miles in Mexico on a motorcycle.
Although I'm a fairly fast rider in the US and ride the same in Mexico I always notice how much faster people drive in Mexico. A 60KPH speed limit in Mexico might be driven at 60MPH. Speed limits are much lower in Mexico but most Nationals drive much faster than the posted speed limit.
Many Nationals are very skillful drivers, fast and sometimes impatient, but skilled.
In all the years we've traveled in Mexico - first in an RV and now on a motorcycle the only time I felt overwhelmed was in Acapulco about 5 years ago. We just revisited Acapulco this March and I felt much safer than I did then.