My wife and I are both 56. I am an artworker with 20 years experience creating digital print and my wife is a childminder.
Are there job opportunities at this age ?
To get you started I suggest taking a look at this Expat Check List. While it isn't specific to the USA or San Diego it does give you lots to think about before making the move.
San Diego has a strong economy and there are lots of job opportunities, especially in the technological sector. While age can act against you when it comes to applying for jobs, just remember that your experience will put you ahead of those who are only just entering the industry.
For more information check out the Working in San Diego page.