From Guate City, I took one of those chicken buses (for the adventure factor ), but there are shuttle buses or vans readily available if you want comfort.
Jaco in Costa Rica, on the other hand, is not the best beach area. It's just like Batangas or Cavite. I'd recommend Guanacaste (where Tamarindo is). And, oh, spending NYE in Costa Rica is a bad idea; nothing spectacular really. That's why I'd rather spend my holidays in the Philippines. Hehe.