ANTIPASTOTECA DI MARE ALLA VOLIGA. My personal winner.
It will cost you a cab, since it is in the city centre but pretty uphill (and there's no parking place). If you don't book it won't be easy to find a table. Best part is that the place is all but recently refurbished, the owner reminds me of a pirate who came back after 20 years at sea, and by the time you'll be done, you'll have to send your clothes to the laundry. The whole point is about food itself: the best fish i've ever had. Go for the "antipasto misto" and the (award winning) "brodetto di pesce", plus anything else which tempts you. Really cheap prices, super experience. Plus, I love this guy. Tripadvisor rates it 5th out of 645 restaurants in Trieste. My cat on drugs would have done a better job at building their website, but it gives you an idea of the flow of the place.
Food is good. Fish. They go for the "best raw material" policy, and it can be sensed. Prices are not the cheapest around, but the message I have to get to you is: I've lived in Trieste for 30 years, I'm used to the sea, I'm used to the sights it has to offer, I see breathtaking sunsets almost every day, but every time I eat here it is as if I discovered everything all over again. The location is unbeatable: Coastal Road, terrace facing right towards the horizon. Tables are few, and people tend to behave, so you can really enjoy the atmosphere. Plus, if you've rented our Tenda Rossa villa, you'll be able to walk home.
Just go for it. I have no clear memories of the place because every time I end up drunk as fuck. What else should I say other than "Tuscan specialities"? If you're here on holidays it makes no sense not giving it a shot. It is not walking distance: either you have a GPS and know how to park in steep roads, or you might go for a taxi (+39040307730), which will cost you 10-15€. Taxi means you can drink, and it's worth going for their cellar. Food is simply excellent. No need to tell you why, just trust me.
If it's winter just forget about it. It gets jammed with people, everyone raising their voices over the neighbor who's raising his voice. You might as well go to a Justin Beiber concert. If, on the other hand, it's summer and the external area is open, you'll find yourself so close to the sea, that if it gets rough you'll end up with salt water in your plate. Food is fine. You can order anything (which isn't always good news), but I used to dine there with my family - so I'll be partial. Ask of Billy, give him a hug. Once you're all stuffed with food, go for a walk in Barcola at night. Walk past the fountain and bump into the "Barachin de Barcola": a small wooden house among the trees which serves shitty wine but gathers a unique atmosphere: people of every age sit or lie down on the floor, by the sea, waiting for a falling star to pass by. Once you're drunk enough, call a cab go home and make love.
This is a hardcore option. A buffet. it should be - along with "Pepi" - our most typical cuisine. It's exactly what you eat in Germany and Austria. (Excellent) bolied meat plus anything else which goes with it. Winter = no place. Summer = you get to sit on the tables in via Torino. This means you're in the epicenter of nightlife hell. Get the timing right, and you'll have fun. Look up Piazza Venezia on Google Maps and anything which goes from there to Siora Rosa means drinking area.