Very scant info. Are you going there on vacation? Are you going to live there? have you heard something that worries you? Costa Rica is the most stable and safest country in Central America. there are thousands of Americans and Europeans living there. Just use the same good common sense you always use and you will be fine.
Worry about bugs and lots of them. Other than that, just act like you do in any big city and use common since. You'll be fine.
the spelling police