I just went ahead and did it at the roller coaster tracks before north coral. The area where you flip the switch, every fight has 5 enemies of either 5 of the red worms lookin dudes or 3 worms and 2 birds. Just took an hour and now i got the buggy and backtracked and got the mythril and just broke down at cosmo canyon. So shouldnt be much longer til I get tiny bronco and go back and get it.