Great thread! Great posts! I agree with most of what's been said.
1) I too like to get in a quick fixed price session at an MP when I first get down to help avoid the tendency to think with my little head later on when I next end up running the gauntlet at the BM.
2) Though I like a little variety as much as the next guy and like to add something new to my menu each visit, I would say at least 1/3 of my sessions are repeats with past favoritas, 1/3 are sessions with potentially new favoritas with whom I hope will be worthy of repeat performances and only 1/3 are solely for variety. Becoming a regular with any girl is more likely to lead to more relaxed pricing on her part, even the occasional freebie. And there is also the non-financial aspect that the increased rapporte that has been developed leads to more relaxed and enjoyable sessions.
2a) On a related topic it also might help in your initial negotiations to give the new girls the idea that there is the posibility of repeat business. Let her know that you're going to be in town for a while (perhaps even if you aren't). And definitely let her know you're a regular visitor to CR. This lets her know a few things. First that if she does well there could be repeat business well into the future. But it also tells her that you might be "plugged into" the network of CR Mongers

and that a thumbs up or down could at least to some degree positively or negatively impact her business

and that you didn't just fall off the turnip truck and probably won't be as susceptible to the scams chicas commonly use on newbies.

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3) Your rule of thumb of $50-60 for all night may be a little on the strict side. The more common rule around here is "No CIEN para solamente una hora". Fifty to sixty
for an hour may not be such an unreasonable standard, but that would usually eliminate chicas such as Roccio. So sometimes rules are meant to be broken or at least bent. While it is a worthy goal, to expect to always pay only $50-60
for TLN would be very difficult for most guys. My own rule is to shoot for $40-60 for one hour and no more than $100 for all night. If a CIEN girl is really hot and my little head is doing the thinking, I'll negotiate for something less than $100/hr, usually $60 but never more than $80, and I'll never go for a TLN with her type as it simply ain't worth it for either of us.
3a) On another related topic, along with "No Cien for an hour" and "Never pay upfront, "Always be ready and willing to walk" should be one of our mantras. Often that is what it takes for her to suddenly start negotiating in all seriousness when she sees her deal slipping away. Unitl the moment you walk, she is likely to think she has the upper hand.
4) I NEVER pay upfront, though I must admit there have been times when faced with this demand after getting back to my room that I have acquiesced by showing them I have the money or placing it on the night stand. Almost always this has been a mistake, even if they haven't actually gotten the money, the simple fact that they are so insistent about it on their end should have been my clue that their attitudes were just not right. All this goes to show is that even a "CR Vet" like myself can make mistakes.
5) I also agree that when they throw out a ridiculous offer like "CIEN para una hora", one should immediately let them know that you know how ridiculous that amount is and counter with a lowball offer of your own. The trick is to make the offer high enough not to make them roll THEIR eyes, but low enough to give you negotiating room to come up to a reasonable amount. Never offer first what you expect to end up paying. Enable them to think that they were able to squeeze something extra out of you. That way everybody wins.
6) As to the merits and drawbacks to MP's, I agree somewhat with both posters. There is a time and place for different alternatives. MP's are great for during the day when pickings are slimmer at some of the bars or when you don't feel like having to negotiate. They're also good for those occasions when you need an on premises alternative. OTOH, the girls may be more heavily "trafficked" at such places and the atmosphere sometimes leaves something to be desired. But for the most part Buzz's objections are reasons to limit his use of MP's but not necessarily rule them out entirely. Personally, I like to vary my diet - some MP's during the day, prospecting for new girls at the BM in the evening or just enjoying the show, checking out tico joints for better deals or using my somewhat limited network of contacts from prior trips.
7) Finally, while I appreciate the issue of power and control in picking vs. being picked, I would like to add a caveat. DR girls that approach are more likely than not hard core pros that have learned to be aggressive. But it is nice to find someone who seems to be really into you. I like to look for the girls who give me some eye contact first, though who don't necessarily approach me. I like to think that means they are interested but perhaps a little shyer than many of the other girls because they are newer at the game. Then again, maybe they think THEY have more control if they make US pursue THEM. Who said game playing was limited to gringas?