Coronado is probably one of the safest cities in the world. The biggest danger is the sun and surf.
Especially during the early months of summer when we have what is called May Grey or June Gloom in the mornings until, usually after noon time there is danger of burning. Even those days that seem to be an over cast, it is important to use sun screen. Clouds offer no protection from UV rays.
Often times there are strong rip tides around here, or other conditions that may be a danger to swimmers. It is important that you follow the advise of the life guards whether you are a strong swimmer or not.
Be carefull not only on the beach... especially when you are white like flour = like me at the beginning of my USA trip.
Long sleeves recommended even in April.
This is not warm Carribean Sea, this is the Pacific Ocean, so do not expect to bath (unless you are a sea lion) in April or May. Although... if you wish.