The City of Costa Mesa has put out an education video about coyotes in the city with assistance of the Costa Mesa Police Department. You might have see the coyote warning signs around town especially by areas close to the Santa Ana river but you yourself might never have seen one and, wonder if they are really around.
I have seen coyotes myself several times in Costa Mesa they look like small dogs and generally are afraid of people. That being said i would be careful if you have small kids or animals. I have seen coyotes often around the Santa Ana and, even during daylight hours in Wilson Park. At night you can often hear the coyotes howl as they make the way down the river also i have seen the animals at Harbor and Wilson in the early hours of the morning. Even though you might not have seen coyotes i would take the advice in this video as they are around the city .