El Salvador has a small but vibrant music scene. For a large sample of the music we have in the country, check out musica.com.sv where you can see a listing of all the most popular bands from the country and listen to their music.
There's a massive reggae-ska movement here and shows consist of kids of all ages moshing, zoot suits, and good vibes. One of the biggest bands to come out of El Salvador in this genre is Adhesivo, and you can find them playing often throughout the country. wtf-elsalvador.com/calendar will have all their shows listed. Another great Salvadoran reggae-ska band is Los Tachos. You can find great reggae culture and music at Trenchtown Rock Bar and Restaurant in Santa Ana, check out their facebook page for shows and much more.
Friguey (pronounced much like "freeway") is a rock band that fuses cumbia, salsa and reggaeton into their rythms. They have songs on the local radio, and you'll probably hear them played throughout the country. Their website lists all their shows and gives more information about them.
For a taste of revolutionary music from the war, Vladimir Cerna is a great example, you can check it out on you tube here: https://www.youtube.com/watch?v=eYoWWsj1Zdk&feature=g-
And of course, El Salvador offers classical mariachi music as well throughout the country. These musicians from Ilobasco are a fun example, although others wandering the cities sport fancy suits and lots of tassles and shiny leather: http://youtu.be/nl6Q7UzCLms