I thought I would comment on the three areas that some have issues with when the go on that dream trip.
If you go to an area that is warm there will be BUGS! Most resorts have great programs to control bugs. Some do not. It you book an unknown or low rated resort this may be an area that has been cut back or they may rarely control bugs. Even at the best resort you may find a bug or two. After all you are in the tropics and the surrounding areas are full of them!
Plan to bring bug spray. If you want to tour the ruins in the middle of the jungle you will need it. Some beaches have sand fleas, files etc. Why go thousands of miles away from home and not be ready for this? Yes, in many places you can by bug spray but the cost is many times what you will pay at home.
There are bad people in every city in the world. But there are many more good people in the world. Just like in your on home town there are places that you may not go to. Ask your resort if you have any questions. If you take a taxi ask the resort which taxis to take. If you would like to venture out on your own ask a local. They want you to have a great time and will steer you away from those areas that are not great.
Protect your valuables! We have traveled all over the world and have never carried our wedding rings. We just don't want to worry about losing them. If you leave money or other valuables in your room not locked up you may have issues. Many of these folks get paid very little. Most are very honest. But just like your home town their is always one bad apple. Don't let these people spoil your trip. Think about what you are leaving laying around. Ensure you safe is closed and locked.
Weather happens all over the world. No way to know if will snow, rain or stay sunny when you are on your trip that you booked months ahead of time. Let you travel agent know your concerns. Afraid of hurricanes? Discuss cancellation insurance with your travel agent or pick an area that has had no direct hurricane hits if you must travel to the Caribbean in October. Make the best of your trip even if weather happens. Talk to your resort about additional ideas of what to do if the weather turns bad. Try this link for information on Caribbean storms:
http://www.stormcarib.com/