San Diego has some great newer properties, but don't discount the many wonderfully renovated older properties. What you'd want to look for are updated systems, like plumbing and electric, that won't have as many problems.
When buying a second home in the same city in which you live, it'll have to make sense to a lender. Living in San Diego, you'd need to buy a home on the beach or on a golf course, or something unique to be able to qualify it as a second home. There are a few condos at the beach well within your price range that you could possibly use as a second home and investment. The HOA fees vary, one is an REO.
So, look within walking distance to a beach, or somwhere it would make sense to buy a vacation home in the same city you live. Barring any rental restrictions, you can always rent it out.