As an HR professional with expertise in global recruitment, I recommend utilizing specific job sites tailored for IT-related roles in London and San Diego. For London, popular platforms like Reed, Indeed, and Totaljobs are widely used for posting IT job vacancies. In California, particularly in San Diego, websites such as Glassdoor, Dice, and ZipRecruiter are known for their IT job listings. Leveraging these specialized platforms will help target the right audience and attract qualified candidates for your IT-related positions. Additionally, consider posting on industry-specific job boards and utilizing social media platforms to broaden your reach and attract top talent.