I agree with Ydogi and Thirdworld on negotiation tactics also have a lot to do with if you live in CR (or a frequent visitor) versus a person who visits once or twice a year for 4 days each. If you are a resident or a frequent visitor, you can afford to "plant the seed" by just chatting up a chica and maybe catch her next time. I think this sometimes work when a girl is hard on a price. She knows (if she remembers you) that you walked away from her fine piece of machinery once. If the flirting/conversation was good the first time, she might actually WANT to go with you. If you did a bad job the first time or she's still hard on the same price next time, well, I think it's time to say NEXT.
Now if you only visit once or twice a year, you probably would like to make the most out of your stay. Planting seeds may not be much of a choice (maybe for next day). Also, it is more difficult to learn another language if you are not exposed to the language all the time. I think your instinct as Pops pointed out would become a key component. Asking for advise to veterans about chicas can be very helpful.
I can tell you for sure I wasn't thinking about the future engagement when I first went to CR. I wasn't sure if I even go back (well I went back 2 months after
). Hell, my buddy and I were trying to break each other's record per day
One thing I did (and still do now) was to stay polite and flirty at the same time and most of all, have fun your own way. Laughter and smiles go a long way...