I think the problem happened with Mmbster because he didn't choose a traditional BG, or in this case an SG who stands in one spot waiting for you to walk by. Usually an SG will stand in a spot with other SGs nearby. (BGs always work inside a bar.)
It' sounds like this girl was a walker, or not even that, but actually was a rip off artist pretending she was a hooker to unsuspecting mongering tourist. It sounds like he was on ART 123 between Revolution and the start of the zona?
I been hearing a few things about girls like this, or worst guys telling you they have a hot girl, and to follow them. You never want to do that, as it could be a set up for a robbery. I make it a point to not talk to anybody in the street, and I never let a girl choose me, I do the picking.
With SGs, you can't always request to pay after, as many or most SGs won't go along with this request. Some of them are so bad, if you pay them $20 it means one position, and you ask them for doggie, they say $5 dollars more, and sometimes you have to stop what you are doing, and actually give them the $5 dollars or it's no go. But it's only $20 dollars, so really I don't care. But yes with BGs always try to insist on paying after, and if they say no just leave, as most hotel will let you bring up another girl for free, if you tell them what happened.
In all my years in Tijuana I have never have a chica rip me off. I mean stealing from my wallet, or running off with my money. I have had a course bad sessions, and one or two SGs promise me something, but then later tell me she never said that, but nothing major, and I have only heard of a few incidents where the girls actually steal money. ( I'm not counting the sob stories the chicas tells their pretend boyfriends in the bars. I'm not talking about the suckers here.) Now in the US I had incidents like what happen to mmbster happen to me.