I've read your thread and it's interesting to me as I'm a Berumen from my father's side. From Jerez, many Berumen moved to Chihuahua, where they can still be found. Some of them in medicine, practising as physicians. A week ago I also saw a Rancho Berumen near a little town called Avinos, in Durango state. And I just heard about Miguel Ángel Berumen, a historian in Ciudad Juárez, who has published books on Pancho Villa (see http://rancholasvoces.blogspot.com/2006/10/libros-mxico-presentan-pancho-villa-la.htmlhttp://rancholasvoces.blogspot.com/2006/10/libros-mxico-presentan-pancho-villa-la.html ) and other titles, I think.
My family branch came from Chihuahua to Mexico City, where we live now.
I had heard the version related to Berumen coming from Bremen, and the ancestors from Germany, but no one in my family really quite believes it. Only an uncle who unfortunately passed away and was an admirer of German discipline.
The other version I'd heard, somewhat stronger, is that the first Berumen who arrived to Mexico in the late 1600's or early 1700's where Sephardi Jews, as many other who converted and came to work in the shadows of the New Spain's mines, where the Regal law was weaker. Two brothers went to Nayarit, and one of them, known as "El Loco", went afterwards to Jerez. This version was confirmed to me recently by a genealogist in Zacatecas, who also said that the original form of the name was Berumes.
One of the most renown Zacatecan and Mexican poets is Ramón López Velarde, whose full name is Ramón López Velarde y Berumen. According to one version, he was the grandson of the Jerez's cacique Marcelo Berumen, not a nice person, who forbade his daughter to marry Mr López Velarde Sr., and that'd be the reason why the poet never used "y Berumen".