Google did not turn up anyone named Sylvano R. Ramos. Neither does the Texas Handbook.
The University of Pennsylvania sheet music collection has "En el Rancho Grande," Uranga and Ramos, Marks Co., no date, and also in the collection "Pennsylvanians," stock arrangement, Uranga, D., E. B. Marks 1934.

Uranga worked on Mexican films in the 1950s and is known as the author of the song "El negra noche." "Alla en el rancho grande" was a Mexican film of 1936 with music by Uranga, Del Moral, Ramos and Tito Guizar. Sheet music with English words, Uranga listed as music author, came out in 1934.

These dates are after unattributed publication of the song by the Texas Folh-Lore Society in 1931.