Antalya is "open' for tourists all year round but a little bit less crowded in the winter.

I cannot give you much info on night-life (too old).
There are bars and discos in the old city, Kaleici and also the area known as Beach Park which is situated behind Konyaalti beach.

There are other people on this forum who live in Antalya. They will no doubt drop by sooner or later.

Try this website, http://www.expatsinantalya.com/main.htm, there is a lot of info on here and also members who are younger than me who should be able to help you.

Enjoy your holiday.

You could do worse than bar 20 on the beach opposite the Porto Bello hotel for a few beers and a quite night (its my second office ) But there a lot of bars in the beach park on the end of konyaalti beach and also the Jolly Joker half way along the beach and the 'irish bar' near the sea life hotel.