It's nice to see my fellow countryman on this board.Here are my answers:
1-Avoid them at all costs.You will be swarmed by them at Nanjing Road.Also there are some near the Bund area.Just say bu yao (don't want) and walk away.
2-Don't invite them to your room.For other girls, general rules apply.Watch out for your drink, keep your valuables in your safe.
3-Depends on who you call i guess.I heard things like a mamasan keep sending girls (like 10 of them) to a guy and charging him 100 RMB for each girl just for taxi.So he ended up paying 1000 RMB just for seeing the girls.
4-Most of them won't care.I asked for massage from my hotel spa in 5 mins later i was offered HJ by the girl, after the massage ended; manager informed me that he could provide "special service" for me.There are guys lurking in front of hotel stairs giving away brochures of girls, and offering ladies to your room.And i was not staying in a lousy sex hotel, it was a pretty well known 4 star hotel.
Mate; in China you should really don't need to worry too much about sex.Shanghai was not exactly what it was used to be after the expo, but there are still many many girls around.Despite all the horror stories i found the city very safe.You just need to be a bit careful, if you survive in Istanbul, SH is a piece of cake.
If you intend to stay 10-15 days and not very old, its very possible to find a regular girl to date.chinese girls are far more open minded about sex.Not conservative like thai gals.If you are not very old and decent looking you can score with a local.If you have time and patience, you can try dating sites and make connections before your trip.This will make things much more easy.
Don't want to spread links in my 2 nd post so you can pm me if you need help with links.
If you need help about anything else, about nightlife, prices, hotels, how to book them, visa, etc. feel free to ask.
Enjoy your trip.