One of the best sources for information on how safe a region is for US travellers is the US State Department Web Site. Here is the page for Mexico with up to date information.
An excerpt from the site makes me think the answer is, don't risk it.
Gun battles between rival TCOs or with Mexican authorities have taken
place in towns and cities in many parts of Mexico, especially in the
border region. Gun battles have occurred in broad daylight on streets
and in other public venues, such as restaurants and clubs. During
some of these incidents, U.S. citizens have been trapped and
temporarily prevented from leaving the area. TCOs use stolen cars and
trucks to create roadblocks on major thoroughfares, preventing the
military and police from responding to criminal activity. The
location and timing of future armed engagements is unpredictable. We
recommend that you defer travel to the areas indicated in this Travel
Warning and to exercise extreme caution when traveling throughout the
northern border region.
The rising number of kidnappings and disappearances throughout Mexico
is of particular concern. Both local and expatriate communities have
been victimized. In addition, local police have been implicated in
some of these incidents. We strongly advise you to lower your profile
and avoid displaying any evidence of wealth that might draw attention.
Carjacking and highway robbery are serious problems in many parts of
the border region and U.S. citizens have been murdered in such
incidents. Most victims who complied with carjackers at these
checkpoints have reported that they were not physically harmed.
Incidents have occurred during the day and at night, and carjackers
have used a variety of techniques, including bumping/moving vehicles
to force them to stop and running vehicles off the road at high
speeds. There are some indications that criminals have particularly
targeted newer and larger vehicles, especially dark-colored SUVs.
However, victims driving a variety of vehicles, from late model SUVs
to old sedans have also been targeted. While violent incidents have
occurred at all hours of the day and night on both modern toll
("cuotas") highways and on secondary roads, they have occurred most
frequently at night and on isolated roads. To reduce risk, we
strongly urge you to travel between cities throughout Mexico only
during daylight hours, to avoid isolated roads, and to use toll roads
whenever possible. The Mexican government has deployed federal police
and military personnel throughout the country as part of its efforts
to combat the TCOs. U.S. citizens traveling on Mexican roads and
highways may encounter government checkpoints, which are often staffed
by military personnel or law enforcement personnel. TCOs have erected
their own unauthorized checkpoints, and killed or abducted motorists
who have failed to stop at them. You should cooperate at all
I have a close friend whose mother lives near Monterrey and for years he drove down to visit her. He wouldn't even DREAM of doing it now, and he flies instead. It is extremely dangerous in the north, especially near the Texas border.