Do you need an Advertising Agency in San Diego, CA? LocalSpark has found the top marketing companies in San Diego. In today’s aggressive marketplace, it’s essential to seek out a professional advertising agency if you want to be competitive. Advertising agencies help clients with web development, SEO, PPC, social media, graphic design, and additional digital marketing strategies that bolster your company’s online image and outreach. Below, we’ve put together a list of the best San Diego, CA, Advertising Agencies.