Many travelers to Antalya rarely have the initiative to leave the massive resort complexes that line the Mediterranean from there to Side. The water slides, the pool-side bars, the house dj's keeping things down-tempo- such things tend to suck the gumption right out of you. For that reason alone, we suggest avoiding all-inclusive packages. If you want to experience the people and places of Antalya, stay at a backpacker hostel in Fethiye or a pension in the city's oldest neighborhood, Kaleici. At least then you'll be motivated to get out and enjoy the nightlife.
Not that the nightlife in Antalya is on the same level as, say, an Istanbul, but there are a few areas where you'll be assured a good time hanging out with local Turks. In Kaleici alone, you'll find much more than just cultural icons like mosques, towers, and minarets. Get your Turkish bath on at the Sefa Hamami, catch a band at the very popular Roxx or the Simurg Cafe, and go big at Club Ally. Wander down Paşa Cami Sokak or just west of Ataturk Caddesi and you'll have quite the bevy of options for once night falls.
As you move east from the city center, you'll find that many of the drinking and dancing options are located in the aforementioned resorts that scatter the coast. One area that is worth checking out is the street just north of Fener Park known as Fener Caddesi. In just a few blocks there is quite a collection of entertainment options, from shticky bars to raucous dives and upscale dance clubs. It's actually pretty amazing that all of this can exist in such a small space.
Since Antalya doesn't cater to the independent, experiential traveler as much as one would hope, you won't find a ton of locations beyond Kaleici and Fener Caddesi where the nightlife is reliably in full swing when the lights go down. Still, if you can't be happy with two locations where fun is bound to be had, then you should be having your adventures in the New York City's of the world. For the rest of you, Antalya will do just fine.