For me, Ellacharmed's fixes for glitches on the World Lot (roads, sidewalks, etc.) were helpful but not so much the problem residential lots and the port where the Scott houseboat can be found in the beginning. Those all turned out to be mostly hopeless and did need to be bulldozed.
Other things that help, along with Ellacharmed's world and getting rid of those lots:
-- NRaas Overwatch, ErrorTrap, and Register for various reasons, but especially to take care of abandoned boats and the spawning of hundreds to thousands of unnecessary resort workers
-- Disallow wild horses (Register) as they tend to get stuck in ridiculous places and the game goes nuts trying to reroute them
-- Use a testingcheatsenabled command to lift the fog on hidden islands. I didn't have to do this while playing in Isla, but others have reported that it helped them; maybe I was just lucky or wasn't there long enough to see the problem.