My next residence is about a block away from the city’s baseball stadium (estadio de béisbol). A taquilla is a ticket office, box office or a ticket window. Here you can line up to buy tickets for seats in the sun or seats in the shade. One is pricier than the other 😉
“Mala onda” is pure street slang. Technically, an “onda” is a wave, like an ocean wave or an electromagnetic wave. In street slang you might say to a buddy, “what’s up”? or, “Qué onda?”
An “onda” can be good or bad – buena onda/mala onda. Here, the author was probably trying to say, “this is messed up”, “this is totally uncool”, or “I’m getting some bad vibes because there are too many old gringos in my neighborhood”.