Spring break in Costa Rica..where should we go?

I'm going to be studying abroad in Costa Rica next spring, and I'm going with my mom this March for 5 days over spring break just to look at the univeristy (Universidad de Heredia) and the area I'll be living at, and hopefully to do some fun activities with her while we're there. We're flying into San jose, and there's a wide variety of things we've read about that we really want to do..the ziplines, seeing el volcan arenal en eruption, spending some time on the beach, horseback riding, waterfalls..ect. So it seems like there's a lot of awesome things to do there, and I'm really just wondering what's worth fitting into our time there, and what the transportation is like between the places we would be going. In relation to San Jose, does anyone know the closest place to do some of the activities? Which ones are good, how do we get there, and how long would it take? On a side note, my mom is really interested in finding a beautiful place where people do yoga, if anyone happens to know anything about somewhere like that. I know it's a lot of questions, but any advice would be reallyy appreciated!