Alcala was born with a creative interest in designing. He was hooked on comic books in his early childhood, and his interest continued throughout his life. He was so compelled with art that he would start drawing pictures and begin posting them in his school's hallways. Alcala was so determined to pursue his career in art that he dropped out of school as a young teenager to do so. He first received his break by doing various commercials and painting signs. Later, he began working in an ironworker's shop, designing household materials like lamps and household furnitures.
Alcala became a star of the Filipino comics. He was so famous that a comic magazine named after him was published, the Alcala Komix Magazine. Alcala introduced himself to the American comic universe when he created the comic book Voltar in 1963 which was a major success. Alcala won numerous awards and became a worldwide attraction, which led him to work for DC Comics in the early 1970s, doing horror and fantasy titles. He also helped recruiting uprising Filipino artists such as Alex Niño. With his new found success in the United States came a plethora of assignments that made him moved to New York in 1976.
Alcala joined Warren Publishing in 1977 and would draw 39 stories for Warren from 1977 through 1981. His series Voltar would be reprinted in issues 2 through 9 of the magazine The Rook.
In the early 1980's, he moved on to take part in the art more suitable for his creative niche. Alcala went on to pencil popular comic books such as Star Wars and Conan the Barbarian. He also inked Don Newton's pencil artwork in Batman.
By 1990's, his booming career and popularity led him to different projects including drawing animations for films. Alcala also took part with the novel Daddy Cool written by the late Donald Goines, which featureed some of Alcala's artworks. He also worked on the Swamp Thing for DC, which marked his return to the comics business. His contributions spanned on several artistic genres including superheroes, horror, and fantasy.