Well, the origin of Flash varies depending on the comic version. Sometimes it's a lab experiment gone wrong, and other times it's a mysterious force that grants him super-speed. But in most cases, it's a sudden and unexpected event that transforms him.
The Flash isn't usually depicted as Hispanic in the mainstream comic versions. However, there might be alternate universes or specific story arcs where his ethnicity is presented differently.
If Flash joined the Avengers in the Age of Ultron, his super - speed could have been a great asset. He could quickly reach danger zones, evacuate civilians much faster than anyone else. Maybe he could even run circles around Ultron's minions, confusing them and buying time for the Avengers to strategize.