The San Diego airport is only a few miles from the port. I always find it less stressful to fly down the day before. There are many things that can delay your flight. Weather, maintenance problems, late crew, and security issues to name a few. Weather may be good in your area but that doesn't mean the weather is good in other areas.
Look for an insurance policy that will cover pre-existing conditions, have good medical coverage including evacuation, and cover trip delay and trip interruption.