when we where in son parc last holidays I think there are 2 or 3 hire car firms..we went with betacars half way down the strip next to the grocery shop...they were very good and had better rates than the first choice rep could get me with there competitor up the road but you have a choice so shop around and play them off against each other to get a good deal...
I think you would be looking around 30/35 euros a day it gets cheaper the longer you let for...think the min is 3 days...
take care
marsha