When I was a child, before kindergarten and a short stint during 4th grade we lived in El Paso. We would cross over to Juarez all the time, to eat, to get haircuts, to visit family....It was a simple thing.
Later, when I was in high school we lived in San Diego, not far from the boarder. I used to go there all they time, especially to get gas. (remember the gas shortage and you could only get gas on even or odd days depending on your license plate?) Again it was a simple thing, easy to cross.
Funny story, one time I went to get gas, and as I was coming back across the agent asked me where I was born. Now keep in mind that of all the times I crossed, no agent ever asked me that. They asked where I lived not where I was born. Well, I had no reason to lie to the agent, so I told the truth. I was born in Munich Germany. The agent promptly asked me for my green card. I don't have and never had a green card. I'm a naturalized citizen due to my dad being in the Army and was station in Dachau and my naturalization date is the date I was born. Seriously, this agent was not going to let me back in the country! I basically had to relate my life story and eventually the agent relented and let me through. From then on, if I was ever asked that question I responded that I was born in San Diego!