The neighborhood immediately around Hong Kong is safe, but don't walk more than two blocks away at night unless you are REALLY aware of your surroundings (i.e., not drunk or distracted). If you want to go elsewhere in the city -- and I recommend that you do -- take a cab or uber.
Within one block of Hong Kong you have two other "big-time" strip club/brothels and probably 15 smaller ones. Depending on the days you are there, the small ones may be totally dead, or a nice change of pace from the large ones. On a weekend night, Hong Kong, Adelita Bar, and Chicago Club will all be packed with hotties all looking to make the most money they can. Hong Kong has two affiliated clubs that are good when Hong Kong itself is overwhelming (Las Chavelas is connected to Hong Kong, Tropical Bar is across the street).
If you are staying at Cascadas (the hotel associated with Hong Kong), you can take up girls from HK, Las Chavelas, and Tropical. Girls from other clubs will not go there (unless you can persuade them to come before or after their shift or whatever). You'll have to pay $15-20 for a room in that hotel.
The streets around Hong Kong (especially the "callejon" directly behind it) are filled with working girls who are available for a short visit -- it helps to speak Spanish and pay in pesos. Some street girls will go to your room in Cascadas, but most will need you to pay $5-10 for a short time room in "their" hotel.
There are a few decent restaurants in the neighborhood if you want to get out of Hotel Cascadas. And of course the taco trucks are amazing. So you could spend the entire three days in the zona norte and never leave.
But, with 2-3 days in Tijuana, you can easily get out of the zona for some real touristy stuff. It's a major city with 2 million people. There is plenty to do. The big tourist shopping street is Revolucion Ave, and it's a 10 minute walk from Cascadas. They have malls and movie theaters and parks in other parts of the city. The beach is crappy but it's a change of pace and only a $10 uber ride. Tijuana is an up-and-coming foodie destination with some REALLY high end restaurants, if you are into that. Or just stop at
Caesar's and have a salad at the place where it was invented (it's a GREAT excuse for when people ask why you went to Tijuana!)
As far as the LT/overnight situation: If you are ONLY staying at Cascadas, you won't get a LT GFE unless you pay for it. Regular girls won't go to the zona norte. Agencies won't send girls there. You would need a real hotel in another part of the city if you want to do that.
As far as I know, there is no universally accepted dating site. Girls post on Tinder and Seeking Arrangements. There are a few active Telegram groups. But it's not like Thailand or Philippines. Agencies will book overnights, but it's almost always 10pm to 6am, so it's mostly sleeping. FYI, the term for an overnight session in TJ is "TLN", or "toda la noche" ("all night"). ST and LT aren't really used there.
Obviously if you make your own connections you can have better luck -- do you speak Spanish? Of course you can always find a diamond in the rough -- if you spend the time. I've had a few lucky finds where the girl and I clicked and she stayed the night.
I described Alejandra in this post, and I went back to meet her a few months later. But it's not something I've ever been able to plan on.
Message me if you have questions.