I'll just focus on colombian and mexican "words". So, if you are roleplaying another a character from another south/central american country, tell me and I'll help you.
Greetings: Hola, que onda?, como te va?, Buenos dias, buenas tardes, buenas noches. Que hay?, entonces que?, Que cuenta? Que tranza?. --- Adios, Hasta luego, Que la pases bien, Cuidate, Camara, Descansa, Lavatelo, Trucha, nos vemos.
Command words. (Let's go, move it, etc.)
Let's go: Vamonos, veni, vente, 'amonos.
Move it: Hazte pa' alla, muevete, hazte pa' la chingada, quitate.
Give me that: Dame eso, trae pa' aca, pasame eso.
Those are like the most important since we just mix them with our English, there's more useful words though. Some are hard to understand to foreign people but it adds realism to your character depending on where he/she is from. These following words are Mexican and Colombian, just like above. They're all mixed up but they are used in both countries.
Gabacho: It's like saying gringo but in a more "mexican" way. Older people from México use that term more than
gringo. - Mexican.
Buseta: Public transport vehicle, like a bus but sometimes smaller, shorter. - Colombian.
Guacala: Expression of disgust like "Ewww". - Mexican.
Cabrearse: This term is more complex, it's a way of being mad and scared depending on how it is used. Juanito got cabreado and didn't go to Lugo's house. That means he was scared or Lugo got cabreado and fought with Cristobal, meaning he got mad. - Colombian.
Grifo: It's a term used when you are high, mostly high on mariguana. - Mexican.
Cansón: An annoying person. - Colombian.
Harto: It is like saying " a lot" but in a more informal way of saying it. - Mexican.
Dar plomo: Colombian term to say "shoot". But to be more correct, grammatically it should be used as, I'm going to darle plomo a Espino, etc.
Indocumentado: Illegal inmigrant that crosses the border to work in the US. - Mexican.
Fierro: A weapon, gun. - Colombian.
Jacal: Way of calling your house, apartment in a more "humble" way. - Mexican.
Güevon: Way of calling someone an idiot, fool or just stupid. It can be used in a good way too, depending on the situation. Not always used to mock people - Colombian.
Jalársela: Masturbate. - Mexican.
Hablar paja: Talk shit, tell lies. - Colombian.
Judicial: The police, mostly federals. - Mexican-Colombian.
Joder: Way of annoying someone. - Colombian.
Junior: Son of a rich guy, spoiled prick. - Mexican.
Lavaperros: Someone who works with the drugs, mostly in rural fields. - Colombian.
Lana: Money. - Mexican.
Mula: Drug trafficker like a courier, someone who is sent by someone. - Colombian.
Lechuga: Mariguana, weed. - Mexican.
Paila: Undesirable situation, bad situation. Like if you were to lose a bet and you'd say, "What am I going to do now? Paila". - Colombian.
Tanates: A very mexican way to say "Balls" referring to your testicles of course, "Suck my tanates."
Parcero/Parce: Way of calling someone friend. - Colombian.
Lléguele: Way of inviting someone to have a drink, seat or to have someone out of your sight like, Lleguele pinche negro, etc. - Mexican.
Pilas: Being focused. - Colombian-Mexican.
Madriza/Putiza: Ghetto way of saying "beating". - Mexican.
Quebrar: Killing someone. - Colombian.
Mamado: Someone who is very muscular, big guy. - Mexican.
Rata: Someone who is a thief or a snitch. - Colombian and Mexican.
Milpa: A very small amount of terrain, land. It's where farmers, plant their stuff. -Mexican.
Sapo: Someone UNABLE to keep something to himself, synonym of snitch. - Colombian.
Mojado: Despective way of calling someone an illegal person. It's very rude. - Mexican.
Tumbar: Scam or steal. - Colombian and Mexican.
Nave: Way of calling your vehicle. - Mexican.
Verraco: This one has a lot of meaning. It can be used to refer to someone as a mad guy, someone who is good at what he does. Like that Lugo is a verraco. - Colombian.
Neta: Way of saying "It's the truth." - Mexican.
Marica: Another way to call someone your friend. - Colombian.
Nel: No. - Mexican.
Malparido: Way to call someone a faggot, son of a bitch, etc. - Colombian.
Panteon: Cementery - Mexican-Colombian.
Pirobo: Another colombian insult, enemy, etc. - Colombian.
Insults. I'm going to add a few insults that are common here, mexican expressions.
Chinga tu madre. - It literally means fuck your mother but we say it like meaning "Stop fucking around" it is used when you trust the people around you. You don't say that to someone who you "respect".
No mames. This one literally means, stop fucking around. Like stop shitting around, etc. You can say this in all contexts.
Vete a la verga. It means go fuck yourself. It is a rude word but you can say it to your friends if you are VERY close to them as a way of playing with them, fucking around, etc.
Pinche. Its like a verb to connect with an insult, like pinche wey. "Fucking wey".