Del Valle is practically synonymous with modern, central Mexico City. In fact, there are seven sections of the colonia plus the famous Tlacoquemacatl Del Valle that's one of the original settlements. It's a huge area.
Few visitors will realize that nearly all of it was lake bottom during the ancient period. The colonial period saw the area passed to the control of the Marquessate of the Valley of Oaxaca. Eventually nearly all of the territory then became part of the Hacienda San Borja. This was an enormous operating estate that famously produced fruit, grain, and pulque. It was later broken down to several ranches, farms, and orchards.
When a streetcar line reached the area in the 19th century, it's thought to have first posted the name for the station within today's neighborhood.
International visitors are often seen in and around Del Valle simply because it's still a clean, modern, and central part of the City.