Cartel literally translates to "billboard" or "poster". While it can refer to a criminal organization in other contexts, in this song, it's used in a much more innocent and aspirational way.
Gilberto Santa Rosa sings about being a "cantante de cartel," which means a singer whose name is big enough to be featured prominently on a billboard or poster. It signifies a successful, well-known artist, making it an interesting word to highlight the ambition and dreams within the music industry.
Gilberto Santa Rosa's "Cantante de Cartel" is a fun look at the push and pull between an artist's personal desires and the expectations of those around them. He sings about wanting to play "veinte o treinta plazas que todos canten conmigo" [twenty or thirty venues where everyone sings with me], feeling at home with his audience.
But then there's the pressure! His girlfriend wants him to be a "cantante de cartel" [a big-name singer], and his friends want him to be famous. He even mentions people wanting him to be like Plácido Domingo or Jorge Negrete! He's happy just singing salsa and connecting with his fans, but everyone else has grander ideas for his career. It's a relatable story about staying true to yourself while navigating the dreams others have for you.