Old Town Mexican Cafe in old town San Diego claims to have the best carnitas in San Diego. I don't know if their claim is true, but their carnitas are the best I have ever had.
Drive up the 5 and check out those two giant hard-nippled boob electric plant thingies on the coast. Life changing. https://www.google.com/maps/@33.368929,-117.5526934,626m/data=!3m1!1e3?hl=en
Rent kayaks (or a tour) at La Jolla shores, they'll take you into the caves, by the sea lions, and over the leopard sharks. For the best fish tacos, go to: Oscar's Mexican Seafood (best hole-in-the-wall, always busy) 703 Turquoise St San Diego, CA 92109 or Bull Taco Cardiff (overlooking the ocean) 2050 S Coast Highway 101 Cardiff, CA 92007 For beers: Toronado San Diego - a million local (and non-local) brews on tap 4026 30th St San Diego, CA 92104 Any Pizza Port will also have good beer and pizza (Carlsbad location has the best building), Ballast Point Brewery is close to Old Town San Diego, and Stone Brewery if you like IPAs and hoppy beer. I second torrey pines state reserve, you can walk up through the hiking trails, down to the beach, and walk back along the water to your car. balboa park. if you end up in north park, go to Carnitas Snack Shack. Beaches: coronado, la jolla shores, solana beach, encinitas, carlsbad - town centers have more developed, touristy beaches. in between town centers are less developed, more local (less restaurants and bathrooms).
What this person said. Personally, I'd stay away from downtown/ Gaslamp unless you are into corporate restaurants and/or go to night clubs or have plans to go to a Padres game. It's pretty douchy down there after the sun goes down. The coast in La Jolla is gorgeous. OB noodle house in Ocean Beach is really good. They have 2 locations now. Great food and a good beer list. Blind Lady Alehouse has excellent pizza and a good beer list. Encinitas Alehouse has great burgers and a good beer list. Toronado has the best beer list in town. Also good food. If you are into beer, there are many breweries better than Stone in town that don't seat 700 people. Societe brewing company is one of the 2 best breweries in the area. They often have food trucks. If you're athletic or a strong swimmer, take a surfing lesson. La Jolla shores is a good place to learn. If you're young and plan on chasing girls while you're here, go to Pacific beach. Almost everyone that lives there is in their 20s and I've never been anywhere that has more hot girls per capita. But like downtown, pretty douchy area after the sun goes down.
Midway is cool Sarah's Smash Shack is a hoot. Basically, you pay money to get a pile of dishes, and then you get to throw them against a metal wall. A ton of fun. Go visit Petco. It's a really nice ballpark Legoland and Seaworld are fun if that's your thing.