I've posted about this in the past; by all means take
their info but don't give out yours - there is so little percentage in it - guys post about giving out all sorts of info - home #, cell #, home address, facebook info, et al - why?? For what possible purpose?
I can think of a dozen senarios that if they have your info that are not beneficial to you - in almost all cases, its a business transaction, nothing more - you may like them, and vice versa, but they are not friends in the traditional sense - if you doubt me, call one up and say you don't have any $$$$ and see if she shows up at your room - you have a better chance of seeing Jesus.....
While everyone in the USA it seems is all "wired up" thats not the case in Costa Rica - just say you don't have internet or a cell phone, and they will not rase an eyebrow.
PS I "get it" that they change cell phone numbers frequently, mostly due to non payment of the bill - but if you have their e mail address and need to contact them, that should work.
Less info they have about you the better.