Be careful!
That's my main advice. I love adventure, and have traveled to more than 20 countries. Remember that in poor countries the camera you're carrying is the equivalent of maybe 10 years earnings for a local. You might carry more cash on you than people there make in a lifetime. Little street kids in Brazil have been known to kill tourists. Not a great adventure getting into a fist fight with a knife wielding Short Round.
Do the money belt thing if you want. I usually wear cargo pants and keep cash in two of the many pockets. In Brazil and Peru, thieves carry razors and slash open back pockets or backpacks, and snatch and grab.
Keep your passport on you at all times. You never know when you'll be asked to produce it.
Don't wander off. Stick with your group and don't do anything stupid. Ever watch the show "I Survived?" A lot of them start with someone saying, "So the two of us went off hiking into the woods/jungle/mountains thinking we'd be back by dinner." They get lost and ten days later one of them comes back alive. Jungles are especially easy places to get lost.
If you do go off adventuring, make sure you're with someone who knows what he or she is doing. They're prepared, and they make sure everyone else is prepared, too. Compass(es), maps, water, food, shelter, water, etc.
Drink lots of (bottled) water. You'll be sweating a lot. Bottled water everywhere, not tap. Probably a good idea to avoid tap even in the city. Remember microbes can live in ice, too.
I also highly suggest you learn at least a few words and phrases in both Spanish and Portuguese. Please, thank you, yes, no, hello, goodbye, where is the ____, how much is _____. It really adds to the trip, and show locals that you respect their culture and are at least trying. I've done that for trips to Ethiopia, Germany, Spain, Egypt, and elsewhere.
As for clothing, light colored works for spotting bugs. If you're going adventurewear, I hear Buzz Off clothing works nicely. I don't like how it looks on me, though. So I spray my stuff with a repellent that can be used on synthetic fabric. Regular repellents can eat holes in synthetics.
Some of your biggest adventures will probably be trying local food (stay away from streetside food carts), and bargaining for souvenirs. As your local friends about what a good price for something might be, and then have at it. People will probably yell and scream, call you crazy, walk away, etc., and then make a deal to sell you something for a third their original price. Fun stuff.
Okay, reading back my advice makes it sound like traveling is horribly dangerous. I'm just cautious about your first big adventure.
Be aware. Be safe, and have fun.