If you're still looking to gain AP, the dessert by Miranda is fantastic. You fight either a Land Worm with 5 which can easily be killed with a death spell, or a Cactuar that's worth 10. If you're playing the GBA version, be careful not to accidentally fight the jumbo Cactuar! He usually hides out on the south western side of the dessert (away from Miranda), but only after you've killed a few Cactaurs.