However, 2 years ago they moved back to our original country and left me and another family member the house to pay rent.

At this point, for the right house and loan, we'd move almost anywhere.

Are people still investing is San Diego or have the high interest rates and low cash flow moved investors to other markets?

Made a really good payday, the family moved to be closer to their family and a new family moved in with room to grow.

And typically when I have seen people move from Single family investing, the next step is into small multi (5-10), then mid sized (11-50ish), then larger scale (100+).  

.🌎 Right now I'm based in Marin County, California, but I'm at a turning point in my life and figuring out where I want to move to and invest in my first property. 💫 My goal is to buy my first house hack, but I am priced out of the California market unless I want to go the condo route.

The tenant from the unit with the leak supposedly moved out because the leak issue was not being fixed.

Run the numbers with what you would be paying rent elsewhere and once you move out to see the cashflow.

People need places to live and as long as people aren't moving out of the area in large numbers, run the numbers and see if they work for you. 

I would not want to move money from an after tax account to a pre tax account even if allowed.