Since not many people own cars here in Costa Rica, you tend to pass a lot of them walking to town or wherever they are going. They always have some sort of words of encouragement for bikers, usually "duro" (strong) of just "buenas" (good day). Since you know that these people probably do not speak English you can add a little fun to your ride by messing with them. For instance, when I'm climbing a big hill and pass somebody walking and they say "duro! duro!" I like to say stuff like " thanks douche bag" or "how's it going butt wipe" or something like that. They will just smile.
You can't say stuff like "Hi asshole" or "how's it going fuck face" because most people know all the cuss words.....just like I know all the cuss words in Spanish.