Yes, mosquitos can be a problem when you are outdoors, esp. evenings. If you are not used to tropical weather, you may do well to take a few precautions:
Avoid staying outdoors after dark
Carry mosquito repellants with you. If you haven't used them before, do procure them a few days early and try them on your skin to ensure you are not allergic or anything. You can also buy them here if needed.
Keep your body covered - long-sleeved dresses, trousers, socks and shoes, etc. will help.