People speak SiSwati, the native language of Eswatini. I have a SiSwati tutor that I meet with twice a week. I'm not fluent, but I can definitely put sentences together! Thankfully, most people in my community speak English as well, so it's not a survival issue to not be fluent in SiSwati.
We use Emalangeni, which is both equal to and fluctuates with the South African Rand. One US Dollar is about 17 Emalangeni. USD goes a long way here, with street vendors selling meals for about $2 and a night at a hotel being about $20. However, we also get paid for food and transport with that in mind, so my monthly allowance is actually quite small from a US perspective.
A bottle of water costs about E15, which is just under $1.
The best meal I had this week was a Triiple Boss Burger from Hungry Lion (yes, two i's). The burger is stacked as follows: bun, chili sauce, MASSIVE spicy breaded chicken breast, cheese, MASSIVE spicy breaded chicken breast, cheese, MASSIVE spicy breaded chicken breast, cheese, tomato, lettuce, bun. I did the math once, that's 1650 calories. But when you've been eating rice and beans for two weeks straight, there's something about the Triiple Big Boss Burger from Hungry Lion that you just can't live without.