I have done medical work in Nicaragua and I took malaria prophylaxis (which I later had an allergic reaction to) and got the typhoid vax IM, though the live PO vaccine has better immunogenicity. If you can get some antibiotics just in case for traveler's diarrhea that will be good, too. Both times we've gone to Nica at least one person in our group has come down with it, but thankfully we've never had anything worse than that. I think one year someone got stung by a scorpion but she was fine after some prednisone and benadryl.
Each country - each region, even - is different, but there is so much to love. If you go with an open mind and heart you will have a wonderful time. Both times I've been to Nica I've gone to help people, but the reality is that I received so much more than I feel I gave and I learned so much more than I taught. We worked at a local teaching hospital as well as at primary care clinics out in the boonies; sometimes I was amazed at the creativity/ingenuity and impressed with how well they were doing with the tiny little bit that they have. In other cases I was shocked at what I saw - roaches and flies in the wards, patients being talked over as if they aren't there (which happens in the US too, granted), basic necessities such as bed linens having to be provided by the families, and some of the med students stayed on their phones during grand rounds. So it's a mixed bag. There are some astoundingly bright young nurses and physicians (and other healthcare workers) in these places who would absolutely flourish in a place with more resources and/or opportunities for learning.
It's amazing what you can find over-the-counter in these countries. Some of it's legit and some isn't and unless you can read Spanish it can be hard to tell what's what.
1) Watch out for cars & motos. One of physicians that goes to Nicaragua with us calls stop signs 'stop suggestions' because people may or may not stop. Just be doubly careful.
2) Be respectful of the people who live where you're visiting. It's a trip for you, but this is their daily life, so as much as you can please try to keep out of the way of people going about their lives. (It's an easy trap to fall into, I'm not criticising you personally.) I mean simple things like standing in the middle of a street or sidewalk to look up at some nice architecture or something, and you get in people's way as they're walking to work or school, etc. I've been guilty of it too, and always feel like such an ass when I realise what I'm doing.
3) I don't know what your Spanish language proficiency is, but don't be afraid to use what you know. People will appreciate you making the effort.
4) Be prepared to see things you would never see in the US. Either because it would've gotten fixed at birth/in childhood, or because there is simply not the access to resources in more remote areas. I saw rheumatic heart disease in 20 year olds from untreated strep, and I saw children walking around with sats in the 50s with one small cardiac conduit that shouldn't even be present but was keeping them alive because they had ALCAPA (read about it here
, almost never seen outside infancy d/t poor prognosis and/or fairly immediate repair). Some of it will be endlessly fascinating, and some of it will be endlessly heartbreaking.
5) Be prepared to come back with a completely different perspective on a LOT of things.
6) Last, but definitely not least: if you can at all, do some reading about the social and political history of the place you're going to be visiting. In the case of Guatemala, they're not too far removed from a terribly bloody almost 40-year-long civil war, and the US played a part in it (similar story in Nicaragua). It's a good idea to have an idea of what people have been through. Fortunately, people in Nicaragua were to a person gracious and kind, and didn't hold the sins of our government against us as people. Some of their buildings are still pockmarked with bullets, and you can visit ruins of churches bombed with US bombs. It's really devastating. (Not to be a downer, just a realist.)
In all, I am super excited for you and I know you'll have a great time and learn a lot. PM me if you have any questions! I love talking about Central America!