This is a bad idea (traveling around CR with some random girl you don't know).
Read this thread as a starter.What the initial post discusses is an individual who did something similar. And it went to shit. I don't remember all the details and can't find his trip report - but he basically set up to travel with one girl who it turned out was not sympatico with him (or vice versa or both) and then met another in Jaco for a 3some at a hotel that was not chica (unregistered visitor) friendly - the that girl turned out to be less than beautiful, shall we say? Drama ensued. No one had fun.
I would meet the girl face-to-face and lay out terms and conditions up front. At a minimum she's going to expect you to pay for everything and then pay her by the day. You're going to have to lay out what you expect and then have a mutually agreed upon determination after negotiation.
If she has K*ds, that's a complication (who is watching them, etc.). Same with pets.
If she get's unhappy you can expect a sudden emergency at home. And yes, even working girls get unhappy with customers (they are people too).
And think about all the shit that can cause drama... (from both of you).... booze, drugs, and so on. All that needs to be talked through.
And you better be able to communicate (her speaking English or you espanol).