Crossing the border to Mexico?

Nogales ... walk across and you are in town. Decent places to stay on the US side

Sounds like you already know more than the answerers. If you can, yes, park on the US side. Here in Texas (I am not far from Mercedes, I do not know where she crossed, but there is a shopping place called Nuevo Progreso just south a few miles from Weslaco, which is geared for walkers) there are really convenient places to park at modest cost at such bridges.

DO NOT TAKE GUNS OR AMMO! That gets you 5 years in a pig pen.

And, do hang on to your billfolds and purses.

Also, please do not give money to the kids and women begging along the bridge if you have them there. They stop working and school because well-meaning if cruel tourists give them more money for acting like monkeys along the bridge. Eventually the kids aren't young enough to get money, and they have no education, thus often end up in drug gangs. The women decide they don't need a man, and see what I said about kids, because that's where their kids end up with no dad.

Don't try to bring back plants or fruit or garlic or meat or eggs or animals. You never know what customs will reject.

And, please be back before dark.

I was near Mercedes TX when I would cross the border every day on a mission trip. It was a nice shopping experience. We walked across. Take plenty of quarters because you have to pay with those to get across and back across.

do like the Hispanics just climb over a fence. :)