Alessandra,
I agree with William F's post in its entirety.
I am not trying to be a parent of dissuade you from taking a trip. I traveled around the world for much of my 20s and worked as an independent contractor, teacher, writer. I went to many countries people advised me not to visit. I am glad I didn't listen to the naysayers.
As I mentioned in my above post, I am very willing to pass on destinations from my past experiences. It is difficult to recommend one particular style of tent. Between Central and South America, you will be encountering so many different conditions that it's impossible to purchase one tent that is suitable to all conditions. The Peruvian Andes, Patagonia, Guatemalan Highlands, and Panamanian islands are all different beasts. This is why I recommend buying as you go and selling or giving away what you are no longer using. I recouped much of my expenses using this method.
But if you are dead set on selecting a tent before you go, there are several worthy options from Tarptent that should suit your needs. Contact the owner, Henry Shires, outline your needs and I'm sure he'll be willing to help. Big Agnes also has decent offerings. I even used a simple, cheap blue tarp at times. Temps for the most part are not a concern in Central America as it's fairly warm throughout the year. However, once you're in the mountains, that can change quickly. Bugs are a problem year round.
There are limitations to camping solo in the backcountry in Latin America that have nothing to do with the American, or Italian media. That's a fact. As a foreigner sleeping in an expensive tent in rural Nicaragua, you will attract more attention than you prefer. Because of the nature of my personal exploration, I often ended up in remote places looking for surf and hikes. Three masked men robbed me at machete point in Southern Nicaragua, about 40 minutes outside of San Juan Del Sur. I never carry much, so all they got was $10 and my cheap flip-flops. That sucked cuz I had to hike back to town barefoot over blazing hot and sharp rocks. I have experienced similar stories in other countries. These are real things that happened to me, not some hyped-up media report. As William said, there are other parts of Latin America still embroiled in conflict. That does not mean you will have problems, many people do not, but it is food for thought.
It seems to me you are almost describing a thru-hike of this part of the world. Is that impossible? Of course not. I for one think it would make for a hell of an adventure, and probably a movie/book deal the way things are going these days.
People here have been trying to help you, and from what I have seen, have provided many useful, educational links. BPLers have recommended several reputable manufacturers for each item you are seeking. Max made some great suggestions in his first post. Weigh your own wants and needs. If something doesn't work, sell it and try something else. You may have to stay in a major city a week or two to get something shipped to you. My base away from home was a friend's house in San Jose (capital), Costa Rica.