Chris
Have you considered booking a room for the night? As has been said, it's not easy to get about by Public transport late at night, and I guess you'd like to take a drink or two, so a Hire Car might not be a good idea.
Sol Hotels (
INVALID URL have hotels in both Magalluf and Palma Nova, and you can book a double room for one night only on the internet. That way you could take your time getting there, have a good night out, and travel back the next day. I bet it would be cheaper than a taxi.
Cheers
Adam