You could wander across the river, yes. Not that there was very much to see back in the early 1980's. The leaky wood ferry at Boquillas was more popular with the
touristas.
About 40-50 of us lived on the US side full-time.
A buddy had a sign on his porch for the "winter Texans". "
Welcome to Texas. Now get the hell out." He was not with the tourism office or Chamber of Commerce. But he loved to watch Clay Henry, the beer-drinking goat at the Trading Post.
You'd get groceries from the Study Butte Store, and once a week we'd carpool into Alpine with ice chests. That was 120 miles - each way. If you got hurt bad, the DPS helicopter would fly you into Midland. It took about two hours for your body to arrive. Not bad-mouthing the DPS, just pointing out that it was a 250-mile ride each way. You were cautious, and smart people kept that in mind. John at Terlingua Medics was good, but he was not a trauma surgeon.
I lived in an old adobe house upstream from the Trading Post. I could hit a 3 iron from my front door, and the ball would land in Mexico.
I'm not a particularly good golfer, by the way.
I took folks on rafting trips through all three canyons, and backpacking trips all over the Park. I grew up in that part of the world, and understand the desert. Probably why the military sent me to jungles most of my enlistment.