Your girlfriend's house is marked on the map by the heart.
As soon as the girl is picked up, you can, of course, take her on a date.
To bad this benefit doesn't count for the girlfriends Denise and Millie because they don't have a standard meeting point, for that matter CJ meets them in a mission.
The progress needed for sex after a successful date will be canceled as soon as all oysters are collected, after a successful date they always wanna have sex despite the progress.
And when you killed Helena, Michelle, Katie or Barbara by accident or if one of these ladies have dumped CJ than they can be found at their meeting point, but only if CJ owns all 50 oysters.
For Millie,make sure you date her when you using your gimp suit(that black suit you get when you follow her to the xxx somekind shop) while wearing this,she will had that romance in bed with you everytime you visit her.(No need for having dinner or whatever.
When she just came out from her house,she going to say sometime and just that and carl and her will do that kind of stuff)For my pc version,once you did that,you will wear you previous outfit and you could wear that gimp suit at your house again.
Denise is first encountered during the mission Burning Desire for Frank Tenpenny, whilst Millie first appears during the mission Key To Her Heart in Las Venturas.