LA is a big place... what part are you talking about? Downtown, South LA, East of LA (City of Industry), West LA, the Valley? Each of these areas have several clubs.
Also, it's not uncommon to see A-, B- or even C-list porn stars dancing all over LA. With production of porn disbursing to other areas in the last 10 years (Miami, Texas, Las Vegas, San Francisco, Prague, Czech Republic, etc.) there is less local work for active porn stars, especially those who don't want to (or cannot) travel.
Finally, there are two modes for porn stars dancing at clubs: Feature Dancing and just dancing (working). Feature Dancers get paid by the club to appear. The club typically posts ads promoting the appearance and schedules multiple show times for her performances. Porn stars not being featured are just working at the club as an contractor or employee and will be expected to pay house fees, tip outs, etc. just like any other dancer there.
In the Valley, Deja Vu and Spearmint Rhino often have feature dancers (say 1 or 2 per quarter). While Deja Vu, Xposed (which is owned by a former 80's era male porn star), and Synn North Hills sometimes have porn actresses dancing UTR.
In West LA, I've seen porn stars working (not as features) at 4Play, Plan B, and rarely at 7th Veil.
As CJKent says, don't expect to get extras from a porn star ITC, especially if she's feature dancing. BUT - if you are on your game, and have established some level of rapport and trust, some may be open to UTR OTC. I have closed 3 or 4 of these opportunities over the last 8 to 10 years.