score:7
Living in Costa Rica is obviously really, really cheap.
Immigration will accept a wallet full of Euros as "proof of sufficient funds" - any decent bank will have no problem changing Euros, US Dollars or Pounds for Colones. Yuan, Rials, Baht and other currencies not printed in the roman alphabet are less likely.
The taxi driver won't take Euros, but the money exchange counter at any international airport serving Central America can give you enough local money to get you through the weekend. At the usual extortionary rates of course.
You could always take a couple of hundred US dollars, but get $10s or $20s. US$100 are frequently counterfeited, and in that part of the world will likely set off the drug detector.