Basically, my rule of thumb is to pay in the currency you are quoted in to avoid an exchange transaction where the rate used will not be favorable to you. Pay your hotel bill in dollars since the price is always quoted in dollars. Paying in colones will entail a currency exchange (at a higher exchange rate, probably 525+). For example, if your hotel billis $600 and you pay in colones, they convert that to 318,000 (600*530). Dividing that back to dollars at the bank rate (505), your $600 hotel bill cost you $630 paying in colones.
Chicas will take either. At 500/1, nothing lost or gained there. Lets see how long till somebody responds that if the exchange rate is 505/1, you can pay in colones and save... yeah, 500 colones on a $100 session. Wow!!! a whole dollar (well almost... more like 99¢

) If that doesn't convince you to use colones nothing will.
Restaurants and bars (HDR, SL) that quote in colones will accept dollars but at a higher rate.
Souvenir shops usually quote in dollars but you can pay in either, nothing lost or gained there.
Tico stores (incl. supermarkets) quote in colones. Paying in dollars will mean an exchnage and raise your cost.
MP's-New Fantasy- definitely pay in dollars. They quote in dollars (to tourists). They convert colones to dollars at 600/1. That means that the $50/hour sessions costs ¢30,000 if you choose to pay in colones, which is really $60.
HLH-The price is the same in either currency. $49 or ¢24,500. Relax, Idem, and the other Tico MP's all quote in colones. Pay in colones or expect to pay more. I think I remember somebody posting they paid $40 for an ¢18,000/hour session. That's a 10% hit.