Also be advised that if you have an accident and there is an injury to a local person you will not be able to leave until the matter is cleared up. In the long run it is usually better to hire a car with a driver, enjoy the scenery and arrive at your destination relaxed. That said, The more adventurous visitor may want to explore Lombok by motorcycle. If you do choose to do so be advised that you will need a motorcycle driver's license - if you don't have one you may get one at the Police station and you need to wear a helmet. More a tourist thing in Senggigi at night but a staple of transportation for locals in Mataram and elsewhere during the day.
All hotels offer currency exchange but at less favorable exchange rates.
Also, it is better to change your money first, if you plan on visiting the central or eastern Lombok for the day. If you choose to deal with an money changer - here are a couple of points worth remembering. Lastly, be prepared, if you are cashing travelers checks you will need to present your passport for identification and many money changers do not accept cash notes that have been defaced - or are in less than near mint condition. The official exchange rate posted is daily in all major newspapers. Also, rates that are too good to be true generally - watch out for.