If you want to cut cost, go during weekdays.. car rental prices are cheaper.. can get proton bout rm40-50 only. But make sure rent car from jetty, not airport. Weekdays easier to get accommodation too.

Take a taxi there.. should cost rm18 if i remember. While going back, you can arrange to drop off the car at the airport instead.. maybe pay a small fee (bout rm20.. same as taxi fare). You have to calculate and see how many days you're renting whether it is more worth it to rent at airport or jetty.