The places to be seen are Gaslamp and La Jolla for sure. Celebrities hangout at IVY hotel and the club ENVY, also Hard Rock Hotel, and the upscale burger joint, Neighborhood. If you want to see all the places to be seen and blend in like a local use a san diego tour guide service. They'll take you out day or night too all the hot spots. And it's super cheap. They even have tour where you run in a group so you're exercising and seeing the city.  Ask for the 9th Wonder Tour. The number is 619 218 2984. Their rates range from $35 to $200 depending on how much of San Diego you want to see.