Just did this, its easy. I think there are four scheduled a day, the schedule is at monbus.es, with Monbus being the operator. Navigate the web page with translation turned off, or, at least on my Android phone, the date selection function will not work properly. There are other options as well. A number of tour bus companies will ferry you one way. The little gift shop across the street from the bus station sells tickets on these buses as well, drop in and ask. Don't worry, getting back by bus is easy as pie.