I was to all of them but I dont know much about where to get sex. But I guess it will be really easy in Prague. There is a huge porn industry and Prague is well known for shooting of "public videos", many porn actresses and many whore houses, also marihuana is decriminalized, its like Amsterdam of eastern europe. Also, there should be escort agencies, you will get to an adress you will get catalouge with  girls, will choose and they are partying with you in few hours have fun.