There are, maybe, 100 people in Boquillas del Carmen. And there are, maybe, another 100 people, within 50 miles of Boquillas del Carmen.
There are, maybe, 50 people in Boquillas Village on the U.S. side. And, maybe, another 100 people within fifty miles of Boquillas Village (not conting tourists to Big Bend).
The only way across the border at this point is to walk down a trail from Boquillas Village to the river. At which point, there is usually a boatman available to ferry you across the river. Then, if you are so inclined, you can ride a burro (or walk) to Boquillas del Carmen and enjoy a cold beer at the cantina.
From the interior of Mexico, Boquillas del Carmen is virtually inaccessible. Their only contact with civilization is across the river -- where there is a fairly well-supplied convenience store at Boquillas Village.
We canoed the Rio Grande, four days and about 40 miles from the opening of Mariscal Canyon down to Boquillas Village, and saw not another soul for the entire trip. The Big Bend country is unbelievably empty.
There was no POE at Boquillas when we made the trip. If there is one needed at that point, I've no objection to it being the cheapest possible arrangement -- as there will be nothing but local traffic.
You simply can't get there from the rest of Mexico...
You don’t have a clue what you are talking about jackass.