Going from Santa Teresa to Monetzuma is a bit annoying and confusing since bus schedules and bus departure times don’t quite match. But if you have the time it will only cost you approx 1200 Colones. I waited on the road and caught the bus that passed at 12:08pm and got me to Cobano by about 12:45pm. I had some lunch and a pineapple juice at the sweet little bakery, located just up the street from the bus stops. I then got on the bus to Montezuma, which passed at 2:05pm, and got me there at about 2:25pm. All in all, easy and cheap but long and hot, but with this route you can sleep in, surf and still get to Montezuma with hours to spare before sunset – and save yourself ~$15 round trip!! Of course this can all be done much earlier in the day. 🙂
I will note that another traveller was on the bus the same time as me but he went up to the waterfalls and back, while I just wandered town and read on the beach. So fyi, an afternoon trip up to the falls and back by bus in the afternoon can be done with a good pair of shoes and some motivation.