After a day spent boogie boarding, sight seeing, or visiting the whales at Sea World, you can work up quite an appetite. 
There are plenty of restaurants of all types to satisfy any cravings you may have during your stay.

Guava Beach, located at 3714 Mission Blvd. in Mission Beach, offers a fun, loud atmosphere, with a gleaming dark wood bar, an elevated pool table lounge, and a private "VIP" room. Loud music may blare from the speakers (don't expect a romantic meal here) and there are a number of TV's mounted around the room. For game days, explect  the place to be packed with loud fans drinking beer and yelling at the TV. Guava Beach boasts an extensive menu and offers delights such as chicken quesidias and teriyaki chicken. 
 
For a hearty, affordable breakfast, IHOP, or the International House of Pancakes, is open 24 hours a day and offers an array of breakfasts, lunches, dinners, and desserts. There are ten locations throughout San Diego, including one at 856 Grand Avenue in Mission Beach. From the banana macadaminan pancakes to the basic buttermilk, you can't go wrong at a place that boasts to be the house of pancakes. They come fluffy and thick and with an assortment of syrups. The wait staff is friendly and quick, but expect to wait in the morning rush. Two people can have a hearty breakfast for under $20 total.

If you're looking for a place to spend a romantic evening, Taylor's Restaurant and Brewery at 721 Grand Avenue in Pacific Beach offers an open rooftop for dining, with a beautiful view of the ocean. On the more expensive side, Taylor's offers steak, seafood and chicken, along with homebrewed beers  
 
If you're in the mood for pizza, Luigi's, located 3210 Mission Blvd. is a good bet in Mission Beach. Luigi's offers both indoor and outdoor seating and boasts of their "Giant Slices," which are truly giant and big enough for two people for lunch. Other items listed on their extensive menu include a variety of pizza, pasta and salads. 

An inexpensive place for lunch is the Pita Pit, located in Pacific Beach on 4516 Mission Blvd. in Mission Beach. It offers an array of meats, seafood, vegetables, and sauces for you to choose to be folded into a pita. Pita Pit also offers delivery for a mere $2.00 extra, and stays open as late as 3 AM Thursday through Sunday.  

 If you're looking for somewhere trendy, sexy, and cool way to start off the night then head to Confidential, in the Gaslamp Quarter at 901 Fourth Avenue.  This place to so "hush-hush" that the restaurant doesn't even have a sign.  Just enter the door at the corner of Fourth and E Street across from Horton Plaza.  Confidential is co-owned by psuedo-celebrity Andrew Firestone of "The Bachelor" fame and the FIrestone tire/wine/beer empire.  The interior is very modern and trendy with pink and blue mood lighting, white leather booths, and trance/house background music.  This is where San Diego's trendsetter's and the occasional celebrity can be spotted nibbling on items from Chef Chris Walsh's "tapas-style" menu.  The dishes are small but the menu is designed so that  each person orders about 3 dishes and shares with everyone at the table.  The food is eclectic and the presentation is a work of art in itself.   I highly recommend the barbeque shrimp with lemon/scotch sorbet, the coca-cola glazed ribs, and the Indian lamb slider.  After 10:00 the restaurant transforms into on of San Diego's hottest lounges and occasionally play host to private celebrity parties.
 
San Diego's Best:

Burger: Hodad's in Ocean Beach ; Rocky's in Pacific Beach ; Nessy Burger @ the 76 & 15 interchange . 

Pizza: Sauced on San Diego Avenue outside of Old Town; The Venetian in Point Loma; Bronx Pizza in Hillcrest (great for those on a budget); Filipi's Pizza Downtown (also inexpensive).

Mexican restaurant: Casa Guadalajara in Old Town.  Taco Shop: La Posta on Washington St.

Fish Taco: Wahoo's, several locations. South Beach Bar & Grill in Ocean Beach. Point Loma Seafoods (also best fish and chips) off Scott St.

Cuban Food: Miami Grill on Poway Road. Coming soon to UTC.

Seafood: Oceanaire in the Gaslamp quarter.

Upscale Italian: La Strada in the Gaslamp Quarter; Old Venice in Point Loma.

Mom & Pop Italian: The Venetian in Point Loma; Filippi's, several locations, but the Downtown location on India street is better than others.

Mimmo's Italian Village on India Street offers attentive service and a diverse menu in a surprising Venetian St. Mark's Square venue. Starters include a delightful fruit, cheese and meat platter. Salads, Italian subs, eight gourmet pizzas and homemade pastas all please.

Chinese: Mandarin House in Hillcrest; Schzechaun Mandarin on Mission Gorge; Panda Inn in Horton Plaza.

Sushi: Ono Sushi in Hillcrest; Cafe Japengo in the La Jolla Village/Golden Triangle area; Ichiban in Hillcrest on University Ave.  Half-price rolls happy hour between 3 and 7pm, Mon-Fri.  Ra in the Gaslamp.

Thai: Thai House in Convoy in Kearny Mesa.

Steak: Ruth's Chris in either Del Mar or at the San Diego Harbor; or if you think you can cook your own, The Strip Club in the Gaslamp.

Persian: Bandar in the Gaslamp; Dmood on Park near Adams Ave.

Sandwich: Cappriotti's in Hillcrest; Olive Tree Market in Ocean Beach; EZ Jays in Pacific Beach; Beach City Market at Horton Plaza in the Gaslamp. 

Asian Fusion: Red Pearl Kitchen in the Gaslamp; Roppongi on Prospect in La Jolla; PF Changs - several locations

Flavor Fusion: Kemo Sabe in Hillcrest (Asian & Southwestern); Indigo Grill in LIttle Italy (Southwest and Pacific American Indian)

For Fun Atmosphere & Live Music:  D ick's Last Resort (try to win your Lobster dinner in a claw game!) in the Gaslamp

Great for Kids: Corvette Diner in Hillcrest. A very fun and loud 50's themed restaurant.