If you have come to relax in Bali, you will likely need to get around the island, unless you plan to spend all your time lounging on the beach. Let's consider the types of transportation available in Bali:
Renting a motorbike/motorcycle is a very common option. It's inexpensive; a basic automatic motorbike costs around $4 per day. You can negotiate a rate of around 350,000 rupiahs (~$30) for two weeks. More advanced motorcycles may cost more. You can rent a bike on the street, but be sure to haggle! Check the bike for any damage, and if you find something, make sure to point it out.
International driving licenses are highly recommended, but you can get by without them. If you're a woman and have never ridden a motorcycle before, think carefully if it's something you want to do. One fall can ruin your vacation. At the very least, you won't be able to go into the water, and at worst, you may suffer fractures and injuries. Motorbikes are a hazardous mode of transportation!
If you're still determined to rent a bike, ask a friend to give you some basic lessons in a quiet area. Practice turns, accelerations, emergency braking, and more. Avoid busy streets for the first couple of days.
Make sure to get insurance in advance.
Pros of using a motorbike include easy navigation through traffic (Bali has very busy traffic), maneuverability, easy parking, and affordability. Cons include the risk of accidents, difficulty for long-distance travel, limited storage space, and discomfort in the rain.
Be sure to read about how to safely learn to ride a bike!
This is also a very good option for getting around. You can also contact these contacts. On average, car rentals start from 200,000 rupiahs per day. A car is convenient for longer trips, traveling around the island, etc. Air conditioning is a big plus! ;)
International driving licenses are also required. Keep in mind that traffic in Bali is on the left side! It might take some time for you to get used to it. Also, be attentive to the numerous motorbike riders, as they are abundant on the roads and move unpredictably. If you accidentally hit a local on a motorbike, even if they are at fault, you could encounter a lot of problems.
An excellent option for traveling between regions. Here is written in detail about taxis in Bali.
In Bali, there is GrabTaxi, which is the most affordable and convenient taxi service.
One advantage of taxis is that you won't have to worry about driving on Bali. You can walk around, have a drink, and not worry about how to get back, etc.
Taxis in Bali are quite affordable, costing approximately 30-80 thousand rupiahs between regions.
The Go-Jek motorcycle taxi network is developing in Bali. It turns out that traveling on a bike is not at all expensive and fast.
Car rental with a driver-guide for a day.
A very popular option in Bali, costing on average 500-600 thousand rupiahs per day (~$50).
This is the most optimal way to explore the island according to your own schedule. Essentially, it's only slightly more expensive than renting a car, but it eliminates a lot of problems: left-hand traffic, navigation confusion, and the driver-guide will explain and show you everything along the route, etc.
Buses in Bali.
The most inconvenient and underdeveloped mode of transportation in Bali. There aren't many routes, and they are very cheap.
In essence, it's a good option only for those traveling on a very tight budget.
However, it must be acknowledged that there have been some improvements in the bus service in Bali recently.
And forget about bicycles ;) Perhaps somewhere near Ubud or in remote eastern areas, you might be able to get around a bit on a bicycle, but in the southern part of the island, it's very hot, dangerous (due to heavy traffic), and inefficient to use a bicycle.
Conclusion on transportation in Bali
If you're going to Bali for a couple of weeks and you don't have a passionate desire to explore the entire island extensively, you can easily manage with taxis/motorbike taxis and renting a car with a driver for excursions.
If you have a thirst for exploration and adventures, then go for a scooter or a car, but be cautious!