My sister and I got a bus in July from Fethiye to Antalya - the buses run quite frequently - if I remember correctly there were probably around six a day from the operator we used. You need to go to the bus station in Fethiye and book the tickets from one of the operators, this can be done in advance. I can't remember now which operator we used but the man in the bus station was very good and even asked the driver to put us on the correct bus for Side once we reached the bus station in Antalya. (which he did). The journey took about 3 1/2 hours, but it does stop for a break of 15 mins at a cafe so you can go to the loo and have a drink, smoke of whatever. The locals also stopped it once for someone to go to a shop for cigs and another time when a few got off, trooped into a shop and bought bread and drinks!!
There are two routes - the mountain one which is the one we used or the coastal road which I understand takes a couple of hours longer.
Once you are out of Fethiye the bus hardly stopped to pick up or drop off passengers until it reached Antalya. The locals seem to use it as a postal service as on both journeys the buss was stopped and packages were put on and then dropped off at their destination.
Brilliant journey and I would certainly do it again.
