Hi Orgynizer,
first, you will never be sure to protected against rip offs, but you can limit the risk ! The area of Nanjing lu(road) and Tong Ren Lu is very known for girls which are installed to ask for drinks and to accelerate you to drink faster, but if you go there you can find really pretty girls. Please check before if you have a ladyboy or an real girl, at tong ren lu some transes are working. I like to go to Heng Shan Lu, there you wil find a couple of bars and discoยดs where you can meet girls for all tastes. Take care, never go with people which offer you girls on street and tell you you could have the best sex of your live, you will loose all your money there and could have trouble with police.
Hope it helps a little bit,
Regards
pretender0815