Mexico has a reputation for danger and corruption and I'm never sure how much is myth and how much is truth. Thanks
Well, as with any other country it depends where you go. I've traveled throughout central and southern Mexico carrying a few thousand dollars worth of photographic gear plus a laptop and other electronic gadgets and never had problems. And yes, I use public transportation.
That said... I don't have any experience with border towns. However, at the beginning of the year the Spanish tv stations (Univision, Telemundo and Galavision) reported a rise in violent crimes in Nuevo Laredo. I don't know how exaggerated were those reports and I presume the violence is limited to some neighborhoods.
Also, supposedly Mexico is cracking down on the drug cartels, so there are millitary check points all over the country. On one occasion, my bus to the pyramids outside Mexico City was checked by the military. Two soldiers got in the bus and checked every man to see if they were carrying weapons. Again, I don't know if that makes that country any safer.
I would recommend you check out the "Lonely Planet" forum for Mexico. That's what I do before I travel. In those forums you'll find travel reports and comments made by people who live in those towns.
Hope you find the information you need.